Self‐testing for contact sensitization to hair dyes – scientific considerations and clinical concerns of an industry‐led screening programme

Abstract

SummaryThe 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: jacpth01@geh.regionh.dk Accepted for publication 15 February 2012 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

Self‐testing for contact allergy to hair dyes – a 5‐year follow‐up multicentre study

“…Values on the left are based on data in table 2 (n = 20) in Thyssen et al. . Values to the right are based on data in the current study (n = 31).…”

“…According to the minutes from the meeting, a validation study should have been launched by the industry in the first quarter of 2013 by testing selected PPD‐positive hair dye‐allergic subjects and controls, and have been concluded with a study report in 2016. It is surprising that the study was carried out in PPD‐allergic individuals, as this is exactly the major criticism raised previously: this is not the correct target group, and therefore it cannot be predicted how the test will perform in consumers who are have not yet been diagnosed with PPD allergy .…”

Severe facial swelling in a pregnant woman after using hair dye

“…Workers in several occupations may be at higher risk of developing sensitisation to PPD and thus increased risk of an allergic response 10. For instance, skin lesions are frequently reported in professional hairdressers.…”

The hair dye allergy self-test: considerations for treating physicians

“…In recent years, hair dye manufacturers have 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. Although the instructions for use differ markedly between products regarding dose, anatomical location, exposure time and occlusion, the intention is that hair dye chemicals be applied by the consumer on the skin and left for about 48 h before a reading is taken of the test site 6 . We recently investigated the basis for the use and the validation of the hair dye allergy self‐test and clearly showed that the test has not yet been sufficiently validated 6 .…”

“…Although the instructions for use differ markedly between products regarding dose, anatomical location, exposure time and occlusion, the intention is that hair dye chemicals be applied by the consumer on the skin and left for about 48 h before a reading is taken of the test site 6 . We recently investigated the basis for the use and the validation of the hair dye allergy self‐test and clearly showed that the test has not yet been sufficiently validated 6 . Pertinently, we concluded that (i) the self‐test is a diagnostic test rather than a screening test; (ii) the self‐test has been validated only in low‐powered studies of patients with dermatitis and not in consumers, the target population of the product; (iii) no study has evaluated how consumers or hairdressers read and interpret the test sites; (iv) hair dye chemicals left on the skin are likely to cause active sensitization in some individuals if the test becomes widely used.…”