Contact Dermatitis • Review Article COD Contact Dermatitis Self-testing for contact sensitization to hair dyes – scientific considerations and clinical concerns of an industry-led screening programme 5 ´ Jacob P. Thyssen1 , Heidi Søsted2 , Wolfgang Uter3 , Axel Schnuch4 , Ana M. Gimenez-Arnau , Martine 6 7 8 9 9 Vigan , Thomas Rustemeyer , Berit Granum , John McFadden , Jonathan M. White , Ian R. White9 , ´ 11 and Jeanne D. Johansen1 Ann Goossens10 , Torkil Menne´ 1 , Carola Liden 1 Department of Dermato-Allergology, National Allergy Research Centre, Copenhagen University Hospital Gentofte, Gentofte DK-2900, Denmark, 2 Department of Dermato-Allergology, Research Centre for Hairdressers and Beauticians, Copenhagen University Hospital Gentofte, Gentofte DK-2900, ¨ D-91054 Erlangen, Germany, Denmark, 3 Department of Medical Informatics, Biometry and Epidemiology, Friedrich Alexander University, Erlangen-Nurnberg, 4 Information Network of Departments of Dermatology, Institute at the Georg-August Universitat ¨ Gottingen, ¨ ¨ D-37075 Gottingen, Germany, 5 Department of ` Dermatology, Hospital del Mar, Parc de Salut Mar, Universitat Autonoma de Barcelona, 08003 Barcelona, Spain, 6 Department of Dermatology, Dermato-Allergology, CHU Saint Jacques, F-25030 Besanc¸on Cedex, France, 7 Department of Dermatology, Free University Hospital, NL-1081 HV Amsterdam, The Netherlands, 8 Department of Food, Water and Cosmetics, Norwegian Institute of Public Health, N-0403 Oslo, Norway, 9 Department of Cutaneous Allergy, St John’s Institute of Dermatology, London SE1 7EH, UK, 10 Department of Dermatology, Contact Allergy Unit, University Hospital KU Leuven, B-3000 Leuven, Belgium, and 11 Institute of Environmental Medicine, Karolinska Institutet, SE-171 77 Stockholm, Sweden doi:10.1111/j.1600-0536.2012.02078.x Summary The cosmetic industry producing hair dyes has, for many years, recommended that their consumers perform �a hair dye allergy self-test’ or similar prior to hair dyeing, to identify individuals who are likely to react upon subsequent hair dyeing. This review offers important information on the requirements for correct validation of screening tests, and concludes that, in its present form, the hair dye self-test has severe limitations: (i) it is not a screening test but a diagnostic test; (ii) it has not been validated according to basic criteria defined by scientists; (iii) it has been evaluated in the wrong population group; (iv) skin reactions have been read by dermatologists and not by the targeted group (consumers and hairdressers); (v) hair dyes contain strong and extreme sensitizers that are left on the skin in high concentrations, potentially resulting in active sensitization; and (vi) recommendations and instructions on how to perform the hair dye self-test vary greatly even among products from the same company, again suggesting that the basis for safe use of the test has not been determined. If the use of a hair dye self-test to predict contact sensitization becomes widespread, there is severe risk that a tool has been marketed that may cause morbidity in European consumers. Key words: allergy alert test; diagnostics; hair dyes; nickel; p-phenylenediamine; screening; self-test; skin alert test. Contact allergy, defined as positive patch test reactions to common haptens, is frequent in general populations, affecting up to 20% of people (1–3). It is Correspondence: Jacob P. Thyssen, Department of Dermatolo-Allergology Gentofte Hospital, National Allergy Research Centre, University of Copenhagen, 2900 Hellerup, Denmark. Tel: +45 3977 3977; Fax: +45 3977 7118. E-mail: [email protected] Accepted for publication 15 February 2012 300 caused by repeated or prolonged cutaneous exposure to contact allergens, including metals such as nickel, cobalt, and chromium; preservatives, such as isothiazolinones, methyldibromo glutaronitrile, formaldehyde, and formaldehyde-releasers; fragrance substances, such as Myroxylon pereirae, Evernia prunastri, limonene, and isoeugenol; and finally, a wide range of very different chemicals, such as those present in topical drugs, plants, and hair dyes. Contact allergy is considered to be the latent © 2012 John Wiley & Sons A/S Contact Dermatitis, 66, 300–311 SELF-TESTING FOR CONTACT SENSITIZATION TO HAIR DYES • THYSSEN ET AL. stage of the disease, whereas allergic contact dermatitis is the clinical disease. The widespread, and necessary, use of chemicals and metals in consumer and occupational products make human allergen exposure unavoidable. It is, however, imperative to reduce allergen exposure by using chemicals with a low sensitizing capacity and by reducing use concentrations to protect humans from developing contact allergy and allergic contact dermatitis, disorders resulting in poor quality of life, sick leave, and work change (4). Historically, there are a number of examples of contact allergens that have been used in too high concentrations or that have been too potent, resulting in epidemics of contact allergy and allergic contact dermatitis; so far, several have been successfully addressed by regulation of use concentrations or prohibition, resulting in a decreasing prevalence of contact allergy (5). Hair dyeing is very frequent in both women and men (6), and is thus an exposure of general concern. Hair dyes are composed of a variety of chemicals, including strong skin sensitizers such as p-phenylenediamine (PPD) and toluene-2,5-diamine (p-toluenediamine, PTD) (7–10). Contact allergy to PPD is fairly frequent among dermatitis patients, and the prevalence seems to be higher in central and southern Europe than in northern Europe (11–13). The difference is likely to be attributable to the use of hair dyes intended for darker shades in these parts of Europe. In line with this observation, products intended for darker hair were associated with higher use concentrations of PPD when more than 2000 products were reviewed (14). Besides PPD, other potent contact sensitizers frequently cause contact allergy (15); hence, patch testing with a broad variety of chemicals is necessary to perform a sufficient diagnostic evaluation of patients with hair dye reactions. Contact allergy to hair dyes can be very serious, causing not only allergic contact dermatitis but also swelling (oedema) of the neck and face, as well as obstruction of the respiratory tract. The latter clinical picture is not infrequent, and may result in high-dose systemic corticosteroid treatment and even hospitalization. In a study by Krasteva et al., 10 of 34 patients with allergic reactions to hair dyes had facial oedema, and 33 of 34 presented with dermatitis (14). As children and teenagers also dye their hair, a similar disease spectrum is encountered in these groups (16). Besides the severe cutaneous and respiratory complications, the potential systemic consequences of contact allergy to hair dyes are currently unknown (17, 18). The cosmetic industry producing hair dyes has for many years recommended that their consumers perform �a hair dye allergy self-test’ (19) or similar prior to hair dyeing, to identify individuals who are likely to react © 2012 John Wiley & Sons A/S Contact Dermatitis, 66, 300–311 upon subsequent hair dyeing. This review evaluates the scientific basis of the hair dye self-test by examining published studies, describes current practices with this test, and discusses its limitations and the clinical and ethical considerations. Hair Dyes Two main categories of hair dye product should be considered, on the basis of their chemistry: oxidative and non-oxidative (20). Permanent hair dyeing with oxidative products requires three main components – an o-substituted or p-substituted aromatic amine, a coupling agent, and an oxidant – and are therefore categorized as oxidative. Self-testing prior to hair dyeing is recommended by the industry for oxidative hair dyes. In 2006, the European Commission’s Scientific Committee on Consumer Products (SCCP) produced a memorandum on hair dye substances and their skin sensitizing properties. The SCCP assessed 46 hair dye substances, and reported that 27 of these fulfil the EU criteria for classification as skin sensitizers (R43). A further categorization of their skin sensitizing potency showed that 10 of the 27 hair dye substances were extreme sensitizers, 13 were strong sensitizers, and four were moderate sensitizers (21). Approximately 100 hair dye substances have now been assessed by the SCCP or the Scientific Committee on Consumer Safety (SCCS), with a similar range of skin sensitizers. The present review will focus only on PPD (INCI; CAS 106-50-3) and PTD (INCI; CAS 95-70-5). PPD belongs to the family of p-substituted aromatic amines. Toluene-2,5-diamine is also named 2methyl-p-phenylenediamine, which indicates that it is a PPD molecule with a methyl group in the �2’ position. The local lymph node assay (LLNA) in mice is used to assess the potential of substances to cause skin sensitization. The LLNA EC3 value is the estimated concentration of a chemical that is necessary to give a three-fold increase in lymph node cell proliferative activity as compared with vehicletreated controls. The EC3 value for PPD is 0.06, indicating that it is an extremely potent skin sensitizer (http:// ec.europa.eu/health/ph_risk/committees/04_sccp/docs/ sccp_o_069.pdf), whereas the EC3 value for PTD is 0.31, indicating that it is at least a strong sensitizer (http:// ec.europa.eu/health/scientific_committees/consumer_ safety/docs/sccs_o_052.pdf). PTD is also used as a salt, with PTD as the cation and sulfate as the anion, that is, toluene-2,5-diamine sulfate (INCI; CAS 615-50-9), and in this case the molecule is named PTDS. In a recent study, PTD, PTDS or PPD were identified in 96% (n = 117) of 122 hair dye products on the Swedish market (9); 98% (n = 120) were found to contain hair dye substances categorized as potent skin sensitizers (Table 1). Of 25 light 301 SELF-TESTING FOR CONTACT SENSITIZATION TO HAIR DYES • THYSSEN ET AL. Table 1. Hair dye substances categorized as potent skin sensitizers, identified on more than 20% of the labels of oxidative hair dye products on the market in Spain (n = 105) or in Sweden (n = 122) Proportion of products containing substance INCI name 4-Amino-2-hydroxytoluene m-Aminophenol p-Aminophenol 2,4-Diaminophenoxyethanol-HCl 2-Methylresorcinol p-Phenylenediamine Resorcinol Toluene-2,5-diamine or toluene-2,5-diamine sulfate CAS no. In Spain (%) In Sweden (%) 2835-95-2 591-27-5 123-30-8 66422-95-5 608-25-3 106-50-3 108-46-3 95-70-5 or 615-50-9 35 76 32 30 33 50 81 49 35 68 25 25 39 16 82 80 Based on (9, 10). blond shade products, only two did not contain potent skin sensitizers, whereas the remainder contained up to eight potent hair dye skin sensitizers. All 105 oxidative hair dye products examined in a similar study conducted in Spain contained potent skin sensitizers (Table 1); 50% contained PPD and another 49% contained PTD or PTDS (10). In comparison, 16% of hair dyes sold in Sweden contained PPD and 80% contained PTD or PTDS (9). Hair dye products sold in Spain and Sweden typically contained five potent hair dye sensitizers each (9, 10). It is important to realize that PPD and PTD are only two of many frequently used sensitizing hair dye substances, and that the use concentrations of skin sensitizers in hair dye products are not labelled, and are therefore unknown to the consumer. Moreover, hair dyes often contain fragrances and other chemicals that are known to induce contact sensitization. Given all of the above, if a hair dye self-test is applied to the skin, the test person will come into contact with several potent skin sensitizers, as it is currently (almost) impossible to buy an oxidative hair dye product without them. Self-Testing for Hair Dye Allergy The European Cosmetics Toiletry and Perfumery Association (COLIPA) advises hair dye manufacturers to instruct their consumers to perform a hair dye allergy self-test (also referred to as the �allergy alert test’, �skin alert test’, or �skin allergy test’) prior to hair dyeing with oxidative hair dyes. In line with this, manufacturers provide test guidelines in their products, in an attempt to have their consumers perform a test prior to each hair dyeing, to predict whether the colouring will result in an allergic reaction. It is of note that a multitude of different tests are currently advised in different hair dye products, but only one commercial test has so far been validated (the Colourstart®). However, the Colourstart® is not used or recommended in any of 302 the tested products from this study, and the validation has many severe flaws, as we will show in this review article. During October 2011, a total of 20 permanent hair dye products were purchased from stores in seven different countries (Denmark, Sweden; Norway, France, Spain, Germany, and the United Kingdom) (Table 2). We intended to include a large range of brands to evaluate whether the manufacturer recommended self-testing for hair dye allergy, and, if they did, how to do so (Table 2). We investigated the preparation procedure, anatomical site of application, duration of exposure, reading recommendations and the advised actions in case of a positive test reaction. Overall, products from 16 different manufacturers were obtained (Keranove, l’Oreal, Garnier, Cosvalitaly, Wella, Tints of Nature, Syoss, Schwarzkopf, Procter & Gamble, Franck Provost, Boots, Superdrug, Naturtint, Colomer Beauty, Eugene, and Laboratorios Belloch). According to the ingredient labels, 19 (95%) of the products contained PPD, PTD, or PTDS. We found that eight different names were used to describe the hair dye self-test. The most frequently used term was the �skin allergy test’, used in seven products, followed by the �skin sensitivity test’, used in four products. Other terms were �warning test for allergy’, etc. Use instructions showed that the self-test should be applied in the elbow flexure for eight of the products, and behind the ear for 11 of the products; for one product, both locations could be used. For 11 products, the test should be performed with only the hair dye cream, whereas for six products, a mixture of the colour cream and the developer should be used. For three products, no instructions were given on whether to use the cream only or a mixture of the two. For seven products, the suggested amount of hair dye to be applied was largely unspecified, as terms like �a small quantity’ or �a few drops’ were used. For 13 products, the size of the application area should be equivalent to 1 cm2 or a ¤1 coin, and the applied amount was specified as �enough to cover © 2012 John Wiley & Sons A/S Contact Dermatitis, 66, 300–311 SELF-TESTING FOR CONTACT SENSITIZATION TO HAIR DYES • THYSSEN ET AL. Table 2. Overview of allergy self-test instructions provided by 16 different companies, found during an investigation of 20 different permanent hair dye products purchased in seven different countries Amount of hair dye and suggested area size Apply a small quantity No area size suggested Cover with plaster n=1 Apply enough to cover an area corresponding to a ¤1 coin n=4 Apply a small amount with a cotton bud on 1 × 1 cm Do not cover n=5 Apply a few drops No area size suggested n=1 Apply a sufficient amount on 1 cm2 Do not touch or cover n=1 Apply some colour cream on 1 × 1 cm Do not touch or cover n=1 Apply a little of the mixture No size of area suggested n=2 Apply a little of the cream No area size mentioned n=2 Apply a small amount of the colorant with an equal amount of developer No area size suggested n=1 Apply a mixture of the colorant and the developer on 1 × 1 cm n=1 Apply a small quantity of the colorant covering on 1 × 1 cm n=1 Total Re-application suggested Resting time (hr) After it has dried, repeat three times None 48 Red or itchy skin After it has dried, repeat two to three times No None 48 Redness, itching, oedema After 45 min 48 None 48 Not defined n=2 Rash, redness, burning or itch n=3 Redness, irritation or burning After it has dried, repeat two to three times After 48 hr 48 Not defined No After 48 hr 48 Redness, itching, or oedema After it has dried, re-apply None 48 Redness, irritation, or swelling After it has dried, repeat three times None 48 No None 24 Redness or itching n=1 Redness, itching, bullae, or suppuration n=1 Swelling, redness, itching, eczema, blistering, etc. No None 48 Redness, burning, or itching After it has dried, repeat twice None 48 Redness, itching, or swelling No the area’, �a little amount’, �some’, or �a sufficient amount’. For 11 products, the consumer was instructed to re-apply the product up to three times. In one product, rinsing after 45 min was suggested, whereas in two products, rinsing after 48 hr was suggested. In the remaining products, rinsing was not suggested at all. Test readings were recommended after 48 hr in 19 of the products, but after 24 hr in one product. No uniform description of skin reactions was given (Table 2), and in three products, the term �reaction’ was used but not defined. In the case of a positive skin test reaction, the consumer was advised to �rinse the © 2012 John Wiley & Sons A/S Contact Dermatitis, 66, 300–311 Definition of positive allergic reaction Rinsing 20 skin and not to dye their hair’ in three products, and �not to use the product/or dye hair’ in 17 products. According to the instructions, the consumer was advised to �contact a doctor if in doubt’ in one product, �see a physician in case a reaction develops’ in one product, and finally �ask a dermatologist if in doubt’ in another product. In summary, instructions varied markedly, even among different hair dye products from the same manufacturer, and it is our impression that most were not really recommendations, but rather mandatory steps that should be followed by the consumer. It is interesting that some PPD-sensitized 303 SELF-TESTING FOR CONTACT SENSITIZATION TO HAIR DYES • THYSSEN ET AL. individuals tend to keep dyeing their hair despite the risk of developing dermatitis and swelling (22). Hence, the intention of the industry to prevent hair dye reactions through the use of a self-test may not reach its target audience at all. Screening Tests–General Aspects Screening is used in medicine to detect a disease in individuals without signs or symptoms of that disease. This is generally performed in an attempt to reduce morbidity, mortality, and overall healthcare costs. Although screening may lead to an earlier diagnosis, nearly all screening tests may result in false-positive and false-negative results. For these reasons, a test used in a screening programme, especially for a disease with a low prevalence, must have high specificity (i.e. the proportion of true-negative reactions correctly identified by the screening test) and moderate to high sensitivity (i.e. the proportion of true-positive reactions correctly identified by the screening test). The balance between sensitivity and specificity that one should strive for must also depend on the seriousness of the disease, and the impact of early detection on prognosis. The advantage of screening is clearly that one may detect a condition at an early stage, resulting in early treatment and cure. The disadvantages are numerous, and include: • adverse effects from the screening procedure, such as uncertainty, stress, discomfort, systemic side-effects, and chemical exposure; • unnecessary investigations and treatments following false-positive test outcomes, potentially resulting in stress, anxiety, and even morbidity; • a false sense of security following false-negative test outcomes, potentially resulting in a delay in diagnosis. The UK National Screening Committee defines screening as �a process of identifying apparently healthy people who may be at increased risk of a disease or condition’ (http://www.screening.nhs.uk/screening#fileid7942). Importantly, it also states in its definition that individuals �can then be offered information, further tests and appropriate treatment to reduce their risk and/or any complications arising from the disease or condition’. The World Health Organization developed criteria for screening programmes in 1968, and these are still applicable today (http://whqlibdoc.who.int/php/WHO_PHP_34.pdf). However, the UK National Screening Committee provides an updated and more comprehensive list of criteria appraising the viability, effectiveness and appropriateness of a screening programme (http://www.screening.nhs. uk/criteria) (Table 3). 304 Validity of the Hair Dye Self-Test In general, a screening test should be validated by comparison against an established gold standard in an appropriate spectrum of subjects representing the target population. Ten questions have been developed that one should ask when reading a paper that claims to validate a screening test, to ensure that the necessary requirements have been met (23) (Table 4). Hitherto, four studies have attempted to investigate the validity of hair dye allergy self-tests, but only two of them included controls. When a screening test is being evaluated, controls without the condition are considered to be a prerequisite for determining the test’s validity, making two of the studies useless for the purpose of validation. Also, a screening test should be validated in the target population for its future use (in this case, individuals from the general population who intend to dye their hair, and not PPDallergic patients). As this has not yet been done in any published study, one may conclude that the hair dye selftest has been very inadequately validated, and that proper validation in the target population is required before healthcare providers can use the data. The intention behind the hair dye self-test is that the consumer or the hairdresser should read and interpret the reaction. No published study has yet evaluated how well these groups perform, which, again, is a prerequisite in the validation process. Finally, no information is given about unwanted side-effects, such as active sensitization, which is necessary knowledge for healthcare providers. Despite the numerous limitations, we provide a short overview of the four published studies to clarify some of the weaknesses and strengths of the hair dye self-test (Table 5). Krasteva et al. performed an open test in 30 dermatitis patients with diagnosed PPD allergy and 30 sex-matched and age-matched controls without PPD allergy (25). The test material was a marketed hair dye product representative of the current L’Or´eal hair colouring technology, containing 1.8% PPD and six other hair dye substances. It was applied without mixing with a developer. The test material was applied to the retro-auricular area on one side, the other side was used as a negative control, and the hair dye was left open for 48 hr without washing. The reactions were read in a non-blinded manner 1 hr after application, and on day 2 and day 4. About half of the patients in both groups had skin changes characterized by erythema after 1 hr. On day 2, all 30 PPD-allergic individuals had erythema and infiltration, and 25 had vesicles. Three individuals in the control group had erythema and one had a papule, but all reactions were considered to be negative (n = 29) or doubtful (n = 1). On day 4, reactivity had decreased in most PPD-allergic individuals. A major criticism of this © 2012 John Wiley & Sons A/S Contact Dermatitis, 66, 300–311 SELF-TESTING FOR CONTACT SENSITIZATION TO HAIR DYES • THYSSEN ET AL. Table 3. Abbreviated version of the screening programme appraisal criteria defined by the UK National Screening Committee (http://www.screening.nhs.uk/criteria) Criteria for appraising the viability, effectiveness and appropriateness of a screening programme The Condition: • The condition should be an important health problem • The epidemiology and natural history of the condition, including development from latent to declared disease, should be adequately understood and there should be a detectable risk factor, disease marker, latent period, or early symptomatic stage • All the cost-effective primary prevention interventions should have been implemented as far as practicable The Test: • There should be a simple, safe, precise and validated screening test • The distribution of test values in the target population should be known and a suitable cut-off level defined and agreed • The test should be acceptable to the population • There should be an agreed policy on the further diagnostic investigation of individuals with a positive test result and on the choices available to those individuals The Treatment: • There should be an effective treatment or intervention for patients identified through early detection, with evidence of early treatment leading to better outcomes than late treatment The Screening Programme: • There should be evidence from high-quality randomized controlled trials that the screening programme is effective in reducing mortality or morbidity. Where screening is aimed solely at providing information to allow the person being screened to make an �informed choice’ (e.g. Down’s syndrome, cystic fibrosis carrier screening), there must be evidence from high-quality trials that the test accurately measures risk. The information that is provided about the test and its outcome must be of value and readily understood by the individual being screened • There should be evidence that the complete screening programme (test, diagnostic procedures, treatment/intervention) is clinically, socially and ethically acceptable to health professionals and the public • The benefit from the screening programme should outweigh the physical and psychological harm (caused by the test, diagnostic procedures, and treatment) • The opportunity cost of the screening programme (including testing, diagnosis and treatment, administration, training, and quality assurance) should be economically balanced in relation to expenditure on medical care as a whole (i.e. value for money). Assessment against this criterion should have regard to evidence from cost benefit and/or cost-effectiveness analyses and have regard to the effective use of available resources • All other options for managing the condition should have been considered (e.g. improving treatment, providing other services), to ensure that no more cost-effective intervention could be introduced or current interventions increased within the resources available • There should be a plan for managing and monitoring the screening programme and an agreed set of quality assurance standards • Evidence-based information, explaining the consequences of testing, investigation, and treatment, should be made available to potential participants to assist them in making an informed choice Hair dye self-test √ √ — — — Unknown — √ — — — Unknown — — — √ , criteria fulfilled; —, criteria not fulfilled. Ideally all the following criteria should be met before screening for a condition is initiated. study, apart from the fact that it was non-blinded, was the absence of information on the strength of PPD reactivity in the PPD-allergic patients who were included. This is a requirement in validation studies (Table 4). Also, followup beyond day 4 had provided an opportunity to detect late reactions. A non-blinded follow-up study by Krasteva et al. included 34 PPD-allergic individuals [previous PPD reactivity was 1+ (n = 2), 2+ (n = 24), and 3+ (n = 8)] and 49 sex-matched and age-matched controls (14). The open test was performed in the same manner as in the first study, but this time hair dyes with increasing concentrations of PPD (A = 0.1%, B = 0.5%, C = 1.0%, and D = 1.5%) were tested consecutively, and a negative control substance (0% PPD) was included. The PPD-negative control subjects were tested with one © 2012 John Wiley & Sons A/S Contact Dermatitis, 66, 300–311 concentration of PPD. The experiment showed that 27 of 34 PPD-allergic individuals reacted to product A (0.1% PPD), 3 of the 7 remaining PPD-allergic individuals reacted to further testing with product B (0.5% PPD), 3 of the 4 remaining PPD-allergic individuals reacted to further testing with product C (1.0% PPD), and the last individual, without reactions to products A–C, reacted to product D (1.5% PPD). No controls reacted to products A–D. In both studies, reactivity was generally stronger on day 2 after application than on to day 4. Inspired by a PPD-allergic patient who performed inadequate pretesting with the PPD-based home patch test kit Colourstart® (Trichocare Diagnostics Ltd) and who afterwards had a reaction from hair dyeing, Orton tested 7 consecutive patients reporting hair dye reactions with the Colourstart® self-test as well as with the standard 305 SELF-TESTING FOR CONTACT SENSITIZATION TO HAIR DYES • THYSSEN ET AL. Table 4. Evaluation of studies that have attempted to validate the hair dye self test using questions that have been recommended for assessing papers claiming to validate screening tests (1–10, 23) and another point included by the authors (11) Question Criteria judged to be fulfilled for the hair dye self-test? 1. Is this test potentially relevant to my practice? ? 2. Has the test been compared with a true gold standard? + 3. Did this validation study include an appropriate spectrum of subjects? − 4. Has workup bias been avoided? + 5. Has expectation bias been avoided? − 6. Was the test shown to be reproducible? − 7. What are the features of the test as derived from this validation study? 8. Were confidence intervals given? — 9. Has a sensible �normal range’ been derived? 10. Has this test been placed in the context of other potential tests in the diagnostic sequence? 11. Has active sensitization been considered in the design and conduct of the study, e.g. through late readings? − Not applicable Not applicable − Comments The answer depends on who you ask (consumers, industry, regulators, or dermatologists). Industry’s target population comprises consumers who have not experienced any previous adverse skin reaction from hair dyeing. This group has not been tested Criteria met for PPD, as the patch test is considered to be the gold standard. However, no studies have attempted to test other oxidative hair dye chemicals Only the study by Basketter and English (24) included a collection of PPD-allergic individuals with an equal distribution of patch test reactivity. However, women were very overrepresented, and all age groups were not represented. No validation study has been performed in the target population addressed by industry. Again, only PPD has undergone a validation attempt Criteria met, as all who were tested with the self-test were also tested with the gold standard None of the studies was blinded. A major concern is that in none of the studies were the tests read by the target group, i.e. consumers intending to dye their hair None of the studies reported repeated interpretation of test reactions The sensitivity and specificity have not been settled. Please refer to the main text No confidence intervals have been reported. It is particularly important to provide confidence intervals in studies with small samples — — None of the studies attempted to investigate the magnitude of active sensitization, which is considered to be critical for risk assessment purposes PPD, p-phenylenediamine; +, criteria met; – , criteria not met; ?, unknown. patch test (26). He observed positive reactions to 0.1% PPD in 1 patient, to 1% PPD in 5 patients, and to 1% PTD in 1 patient. However, negative reactions to the Colourstart® kit were noted in 4 patients. Later, Basketter and English described a non-blinded study of the Colourstart® kit in 30 PPD-allergic individuals; 10 with 1+, 10 with 2+ and 10 with 3+ reactivity (24). Overall, 19 of 30 patients reacted to the Colourstart® kit; 10 of 10 patients with 3+ reactivity to PPD reacted to the Colourstart® kit, 8 of 10 patients with 2+ reactivity reacted, and 1 of 10 patients with 1+ reactivity reacted. These findings clearly showed that this self-test could only identify those with strong 306 reactivity, and not those with weaker reactions; that is, it has considerable shortcomings regarding sensitivity and negative predictive value. On the basis of the four available studies, the sensitivity [(true positives/(true positives + false negatives)] and specificity [true negatives/(true negatives + false positives)] of the diagnostic self-test can be calculated, although the studies, as mentioned, had critical limitations, including lack of: (i) controls, (ii) an appropriate spectrum of participants, (iii) blinding, (iv) information on reproducibility (27), and (v) information on adverse effects (Tables 4 and 5). The specificity as assessed from the two small studies appears to be very high (100%), © 2012 John Wiley & Sons A/S Contact Dermatitis, 66, 300–311 SELF-TESTING FOR CONTACT SENSITIZATION TO HAIR DYES • THYSSEN ET AL. Table 5. The sensitivity and specificity of the self-test derived from published studies No. of PPD-allergic individuals No. of controls Concentration of PPD, % Sensitivity, % (95% CI) Krasteva et al. (25) 30 30 1.8 100 (88.4–100) Krasteva et al. (14) 34 34 34 34 7 49 49 49 49 — 0.1 0.5 1.0 1.5 79.4 (62.1–91.2) 88.2 (72.5–96.7) 97.1 (84.7–100) 100 (89.7–100) 42.9 (9.9–81.6) 30 10c 10d 10e — — — — b Author Orton (26) Basketter and English (24) b b b b 63.3 (43.9–80.1) 100 (69.2–100) 80.0 (44.4–97.5) 10.0 (2.5–44.5) Specificity, % (95% CI)a Comments 100 (88.4–100) No information was given about the strength of patch test reactivity to PPD 100 (92.7–100) Study results suggest that high PPD concentrations are necessary to increase sensitivity — — — — — The test is not very sensitive in a mixed patient population The sensitivity of the test relies heavily on the degree of sensitization in those tested PPD, p-phenylenediamine. Exact 95% confidence intervals (CIs) calculated by the authors. See the main text for the critical limitations of these studies and where we list factors suggesting inadequate validation. a It is the authors’ opinion that the sensitivity and specificity estimates derived from these studies cannot be used or generalized, and that the studies have very critical limitations. See the text for details. b The Colourstart® product contains approximately 15 μg of PPD applied uniformly across an area of 0.5 cm2 , leading to a dose of 30 μg/cm2 . c Individuals with 3+ reactivity to PPD. d Individuals with 2+ reactivity to PPD. e Individuals with 1+ reactivity to PPD. preventing false-positive reactions. However, it should be acknowledged that false-positive reactions will be expected to appear if the test is used in a population with a lower prevalence of contact sensitization to hair dyes. The sensitivity was high when high PPD concentrations were used or when a strongly sensitized population was tested, but low when weaker PPD concentrations were used or when patients with weaker reactivity to PPD were examined. On the basis of the available data, self-testing in patients may therefore result in very few false-positive reactions but in false-negative reactions of an unknown extent. In this case, one may question whether it is more desirable to have a moderate specificity (as false-positive reactions would, in the worst case, prevent people from dyeing their hair) and a high sensitivity (as false-negative reactions may result in severe reactions that are potentially life-threatening). Hence, it may be considered more appropriate to detect every PPD-allergic individual who would otherwise develop severe reactions to hair dyes than to save hundreds/thousands of individuals from the psychological/social effects of not dyeing their hair. However, this would require an increase in the applied PPD test concentration, potentially increasing the risk of active sensitization to PPD. Given the above, the ideal screening test for hair dye allergy has not yet been developed, but should be both very sensitive and specific but without causing active © 2012 John Wiley & Sons A/S Contact Dermatitis, 66, 300–311 sensitization, a combination that may be very difficult to obtain. The sizes of published studies are inadequate to determine the sensitivity and specificity of the hair dye self-test with sufficient precision. Moreover, there are important aspects of validation studies that have not been addressed properly in published studies, as described above and in Table 4. In particular, it should be remembered that the above data have been generated by testing dermatitis patients and not consumers without symptoms. This means that the figures represent the selftest’s performance as a diagnostic test rather than as a screening test. It is likely that validation in the true target group (healthy consumers) would give quite different values – certainly for the predictive values, which depend on the true prevalence in the target population. It is crucial that screening test validation studies be performed in accordance with high methodological standards, and that the benefits of an in vivo screening test outweigh the risk, which is clearly not the case for the hair dye self-test. Clinical and Ethical Considerations Regarding the Hair Dye Self-Test When the hair dye industry instructs consumers to perform a self-test to diagnose contact allergy to hair dyes prior to hair dyeing, several clinical and ethical considerations should be addressed when evaluating its use and 307 SELF-TESTING FOR CONTACT SENSITIZATION TO HAIR DYES • THYSSEN ET AL. potential consequences. PPD is ranked as �category A’ in a ranking of the allergenic potency of chemicals, which means that �it is a significant contact allergen because of proven strong contact allergenic effect in humans after short and/or almost negligible exposure’ (28). A number of sensitization tests have been performed in humans. Kligman showed that repeated application of 10% PPD sensitized all 24 subjects in a human maximization test (29). Marzulli and Maibach performed a PPD sensitization study using the Draize procedure, and showed that 7.2% of 97 healthy volunteers were sensitized to 0.01% PPD, 11.2 to 0.1% PPD, and 53.4 to 1% (10 000 ppm) PPD (30). Basketter et al. performed a human repeat insult patch test (HRIPT) with 1% PPD in 98 healthy subjects without PPD allergy, and showed that 3 reacted when later exposed to 1% PPD (31). In the same study, subjects were instructed to dye their hair with hair dye products containing 0.5% PPD and applied for 5 min/day on the first 4 days and then once weekly for 6 months (n = 1107) (group 1), or a permanent hair dye product containing 1.5% PPD and applied for 30–40 min once monthly for 6 months (n = 548) (group 2), or no hair dye product (n = 516) (group 3). At the end of the 6-month period, patch testing with 1% PPD showed that the prevalence of PPD allergy was 7.2% in group 1, 1.3% in group 2, and 0.4% in group 3. These data indicated that repeated short-time exposure to hair dyes with a low concentration of PPD increased the risk of PPD sensitization more than prolonged exposure to a higher concentration of PPD, but with a longer time interval. Predictive human sensitization tests, such as the human maximization test, the Draize procedure, and the HRIPT, attempt to induce long-lasting or permanent sensitization in the individual. Because of ethical considerations, the SCCS and the former SCCP share the opinion of the former SCCNFP that predictive human sensitization tests of potentially cutaneous sensitizing cosmetic ingredients or mixtures of ingredients should not be undertaken (http:// ec.europa.eu/health/ph_risk/committees/04_sccp/docs/ sccp_s_01.pdf and http://ec.europa.eu/health/scientific_ committees/consumer_safety/opinions/sccnfp_opinions_ 97_04/sccp_out102_en.htm). Repeated hair dye application on the skin with the consumer self-test may, in its current form, be compared with experimental human sensitization tests. As PPD and other hair dye chemicals are strong and extreme sensitizers, their use in screening tests should be carefully considered and probably discouraged. Clinical and Ethical Considerations • False-negative readings. Positive patch test reactions to PPD may sometimes appear after several days. 308 Hence, when reading of patch tests and allergy selftests is restricted to day 2, false-negative readings are expected to appear to an unknown degree. • Risk of active sensitization. PPD is an extreme sensitizer, and allergy skin testing with this chemical should be carefully performed, owing to the recognized risk of active sensitization (32–37). The concentration of PPD in hair dye products is restricted to a maximum of 2% PPD on the head, calculated as free base, but very high exposure concentrations might be applied in the hair dye self-test. Furthermore, other sensitizers, such as PTD (maximum 4% on the head), and several other extreme and potent sensitizers are used in hair dyes, and may cause sensitization following repeated exposure. Experimental studies have clearly shown that the risk of sensitization increases with allergen dose per unit area, frequency of exposure, duration of exposure, occlusion, the presence of penetration-enhancing factors, and impairment of skin barrier function, and is related to anatomical site (38–40). The hair dye selftest carries a significant risk of sensitization, as can be seen in Table 6. It is important to understand that, as it is the dose of allergen per unit area that is critical for sensitization, application of an allergen to a small skin area does not diminish the risk of sensitization when compared with a larger skin area with the same dose per area. Hence, even though the self-test is applied to a small skin area, it still carries the same risk of sensitization. It is also of major importance that a recent experimental study showed that three exposures to 10 μg/cm2 2,4-dinitrochlorobenzene (DNCB), that is, 30 μg/cm2 cumulatively, led to the same degree of sensitization as one exposure to 60 μg/cm2 DNCB (41). Thus, repeated exposure to low doses of contact sensitizers, as occurs when the hair self-test is performed, may considerably increase the risk of sensitization. In fact, individuals who dye their hair may need to do so at least every 4–8 weeks to avoid noticeable differences in hair colour. In a worst case scenario, an individual performing the hair dye self-test every fourth week applies up to 2% PPD on the skin each time, in addition to other sensitizers in the product. Such gross exposures strongly contrast with the norms of clinical diagnostic patch testing, when the practice is to attempt to reduce repeated allergen exposures from patch testing, owing to the risk of active sensitization. Also, the patch test concentration of PPD has been lowered in, for example, Germany to reduce active sensitization. Patients are infrequently patch tested on more than one occasion, and if they © 2012 John Wiley & Sons A/S Contact Dermatitis, 66, 300–311 SELF-TESTING FOR CONTACT SENSITIZATION TO HAIR DYES • THYSSEN ET AL. Table 6. An overview of factors associated with increased risk of sensitization Factors increasing the risk of contact sensitization Factors associated with the hair dye self-test Allergenic potency Dose per unit area Frequency of exposure + + + Duration ± Occlusion ± Presence of penetration-enhancing factors Mixture of allergens + Impaired skin barrier functions ± + Comments PPD and several other hair dye substances are extreme or strong sensitizers High concentrations are used Hair dyeing is frequently performed, resulting in repeated performance of the self-test Exposure time is variable, depending on the product. It is expected to be short only if hair dye is rinsed off promptly after application, which is not part of the instructions No occlusion if located behind the ear, but possible intermittent occlusion if located in the elbow flexure, and occlusion if covered by plaster Hair dyes often contain penetration enhancers, e.g. sodium lauryl sulfate Hair dyes contain many chemicals that may result in a cocktail effect, increasing sensitization Depending on genetic predisposition PPD, p-phenylenediamine. are, they are tested at most once every 1–2 years. Also, one should remember that consumers may forget to remove the hair dye self-test at the suggested time (in fact, most instructions advise the consumer to leave it on), resulting in prolonged exposure to a high concentration of PPD, again increasing the risk of sensitization. Despite some manufacturers recommending self-testing with a 45 min application of hair dye products, the risk of sensitization remains, as the test involves significant exposure to extreme sensitizers and sufficient time to induce contact sensitization. Thus, short-time exposure can by no means be considered to be a safe or warranted screening method. • Reading of the test results. Patch test reading is complex and sometimes very difficult. For this reason, clinicians undergo specific training in this area, and there is a continuous interest in inter-observer variability in the reading of an allergic reaction (42, 43). A set of definitions have been established by the International Contact Dermatitis Research Group, and these should be carefully followed to standardize readings and distinguish irritant from allergic reactions (44). It is very questionable whether individuals from the general population are able to distinguish such reactions. In the article by Orton, the PPD-allergic patient had not interpreted the Colourstart® correctly (26), emphasizing that this is a real concern. Misinterpretation may result in false-positive and false-negative readings. Hence, as stated, the hair dye self test has not been validated yet, as this would require that consumers (study © 2012 John Wiley & Sons A/S Contact Dermatitis, 66, 300–311 participants) attempt to perform the test readings themselves. • Cosmetic or medicines. Article 2 of the Cosmetics Directive states that a cosmetic product put on the market within the Community must not cause damage to human health when applied under normal or reasonably foreseeable conditions of use (http:// europa.eu/legislation_summaries/consumers/ product_labelling_and_packaging/l21191_en.ht). In the hair dye allergy self-test, one must conclude that the hair dyes are used as medicines rather than as cosmetics. This is something that industry and European regulatory authorities have not yet addressed, but they will inevitably have to do. According to Directive 2001/83/EC [article 1(4b)], hair dye allergy self-tests must be considered as �medicinal products’, as allergens are applied for diagnostic purposes. At present, there is no market authorization, and to obtain this, hair dye allergy self-tests should first undergo clinical trials according to the Clinical Trials Directive (2001/20/EC). Concluding Remarks The EU has more than 500 million citizens. Studies have indicated that hair dyeing is frequent and recurring in many people’s lives. If we apply figures from a Danish adult questionnaire study, up to 80% of women and 20% of men will dye their hair at some point (6). Also, teenagers and even children dye their hair. The general use of a hair dye allergy self-test prior to hair dyeing will therefore result in unnecessary repeated exposure to PPD, PTD and 309 SELF-TESTING FOR CONTACT SENSITIZATION TO HAIR DYES • THYSSEN ET AL. Table 7. Example of abuse of the hair dye self-tests taken from real life in France A healthy young girl without any skin symptoms was seen by a physician, as she intended to enroll in a hairdressing school. The school had given her a printed document that she was instructed to give to her general practitioner for signature. She was supposed to initially visit a hairdresser, who should apply a solution used for permanent curling and a solution used for permanent hair dyeing on her skin. These should be left untouched for 48 hr, and the general practitioner should inspect the skin area for allergic reactions. He should afterwards note his findings on the document and sign it. This proof of �non-allergy to products of hairdressing’ was a prerequisite for enrolling in the hairdressing school. other sensitizing chemicals in hundreds of millions of EU citizens every year, increasing the risk of sensitization. Once an individual is sensitized, elicitation concentrations are much lower, and it is currently unknown whether it may affect the propensity to develop other severe diseases. The vulnerability of individuals to the development of contact sensitization and allergic dermatitis is variable, and has genetic determinants (45). This review offers important information on the requirements for correct validation of screening tests, and concludes that, in its present form, the hair dye self-test has severe limitations: (i) it is not a screening test but a diagnostic test; (ii) it has not been validated according to basic criteria defined by scientists; (iii) it has been evaluated in the wrong population group; (iv) skin reactions have been read by dermatologists and not by the targeted group (consumers and hairdressers); (v) hair dyes contain strong and extreme sensitizers that are left on the skin in high concentrations, potentially resulting in active sensitization; and (vi) recommendations and instructions on how to perform the hair dye self-test vary greatly, even among products from the same company, again suggesting that the basis for safe use of the test has not been determined. If the use of a hair dye self-test to predict contact sensitization becomes widespread, there is a severe risk that a tool has been marketed that may cause morbidity in European consumers. Also, such a test may be abused in different contexts; one example is provided in Table 7. It is worth repeating that the UK National Screening Committee states that, in cases of positive screening test reactions, individuals �can then be offered information, further tests and appropriate treatment to reduce their risk and/or any complications arising from the disease or condition’. No such back-up system is available in this industrially proposed screening programme. It is a political task to debate whether the hair dye allergy self-tests should be removed from the market or undergo strict validation according to the presented criteria prior to release. Another important issue, which we have not addressed, is responsibility. Politicians and regulators should probably address this as well. 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