Is there a role for the PPD skin test when a hair colour is based on other dyes?

by Nick | September 13, 2018 | in

The Association of Registered Trichologists ask world renowned Toxicologist and expert on hair dye safety, Dr David Basketter, whether published scientific literature supports the role of a PPD skin test when colourants is based on other dyes.

The answer is an emphatic “yes”.

In this special scientific article, Dr Basketter explains why.

A number of suppliers of hair dyes base their products on ingredients that allow them to claim “PPD free” or something similar. Consequently, it is reasonable to ask whether a skin test based on PPD has any value for the user of other hair dyes. The answer is an emphatic “yes”; here’s why:

For hair dyes that are not temporary, the dye ingredients are still based on variants of PPD, typically PTD and more recently ME+. These alternative ingredients are still mostly PPD and “cross react” with it very well. Several clinical studies have shown that individuals who are already allergic to PPD are quite likely also to experience skin allergy to related hair dye chemicals such as PTD and ME+ (e.g. Basketter and English, 2010; Blomeke et al, 2015; Schuttelaar et al, 2018).
More importantly still, individuals who are particularly sensitive to PPD, are much more likely also to experience a strong allergic reaction to these PPD variants.
Thus, to be responsible to potential hair dye users, carrying out a skin test to check that they are not allergic to PPD and its variants remains the right thing to do.
Finally, it is worth remembering the cautionary note published recently in the British Journal of Dermatology was that the “advice for patients with hair dye allergy remains stop using permanent hair dyes” (Pongpairoj et al, 2016). This advice was based on the recognition that many PPD allergic individuals would also react to variants such as PTD and ME+.

Manufacturers’ publicity sometimes suggests that use of PPD variants reduces the chance of allergy, but it should be kept in mind that this refers to the theoretical chance of inducing new allergy. The purpose of the consumer skin test is to detect existing allergy, which is where the real risk of an adverse skin reaction to hair dye applied to the head actually arises.