Testing For Hair-Dye Allergy Should Be Done By Docs, Not Consumers – SCCP

Testing to determine sensitivity to hair-dye substances should be performed by qualified professionals rather than by consumers due to the risk of sensitization and false results, among other concerns, the European Commission's Scientific Committee on Consumer Products says.

In a preliminary opinion released July 6, SCCP upholds a 1992 opinion from the Scientific Committee of Cosmetology asserting that sensitivity testing should be performed by "trained dermatologists who will be medico-legally responsible for any problems related to false negative results and active sensitization and who are trained to evaluate any response and can give advice accordingly."

SCC also pointed out that self-tests "may be performed before a first hair dye when allergy to PPD should not be present (no previous exposure), but not before subsequent colorings when allergy may have been acquired."

That opinion compelled the EC to lift an obligation that marketers of certain hair dyes package them with the warning: "Sensitivity test advisable before use."

However, some hair-dye products on the market still carry labeling advising consumers to self-apply a small amount of the substance on the skin - usually behind the ear or in the fold of the elbow - before dyeing the hair to test for allergy to the substance.

SCCP notes that a lack of standardization renders self-testing largely unreliable. A look at two sets of self-test instructions from different hair-colorant manufacturers "show[s] that the procedure allows for large variation of crucial factors that are carefully standardized in clinical diagnostic patch testing."

For instance, the prescribed application time for self-testing varies from 45 minutes to 48 hours, the committee points out. Also, manufacturers instruct consumers to apply "a small amount" of the substance once or as many as three times, SCCP notes.

Furthermore, "the concentration of hair dye substance is not known, as the product is tested 'as is,'" the committee observes. The consumer could be exposed to up to 6-percent para-phenylenediamine (PPD) - the main agent in the majority of hair dyes on the market - or 10-percent Toluene-2,5-diamine (TDA).

Ten percent being "the highest allowed concentration of some of the most potent skin sensitizers," exposure may induce sensitization, according to SCCP. "The concentration may also be much lower than what is known to be relevant in patch testing," yielding a false negative result, the committee adds.

In addition, SCCP says, consumers typically are directed to conduct the test 48 hours before product use - in accordance with guidance from the European Cosmetic Toiletry and Perfumery Association - but allergic reactions may develop up to seven days after application.

The panel also notes that in self-testing, the recommended application site is either behind the ear or on the arm, whereas patch testing in a clinical setting is done on the back for reason of reproducibility.

Moreover, "it is difficult to understand how the test can be performed behind the ear ... by repeated application onto a 1-cm² area and how the reaction other than itching can be assessed by the subject."

Finally, clinical diagnostic patch testing involves occluded - versus open - application of the substance.

"The 'self-test' gives extremely large and uncontrolled variation in dose, duration of exposure and other factors crucial for the outcome. The validity as a relevant test for contact allergy to hair-dye substances is considered very low," SCCP states.

The panel agrees with SCC's earlier contention that as a result of applying an "unstandardized amount of dye to an unstandardized area of skin ... some PPD³-allergic individuals will develop an easily observable reaction, an unknown number of individuals who are PPD³ hair-dye-allergic will develop no reaction - i.e., a false negative result - and some will be actively sensitized by the procedure."

SCCP recognizes that self-testing can benefit those who perform the test, develop a positive reaction and therefore avoid more detrimental use of the product. However, "the proportion of hair-dye-chemical-allergic individuals who do produce a positive reaction from this in vivo diagnostic test is unknown."

Recent research has shown a dramatic increase in recent years in positive reactions to patch testing for allergy to hair-dye substances among adults presenting in clinics with contact dermatitis (¹ (Also see "Could Growing Prevalence Of Hair-Dye Allergy Necessitate New Regulation?" - HBW Insight, 12 Feb, 2007.), p. 4).

- Ryan Nelson ([email protected])