Hair Dye Alternative Named Allergen of the Year

A chemical compound used in many permanent hair dyes has been named Allergen of the Year for 2src25 by the American Contact Dermatitis Society (ACDS). 

Toluene-2,5-diamine sulfate (PTDS) is an aromatic amine that causes allergic reactions in some individuals, but it can serve as an alternative to paraphenylenediamine (PPD) for others, according to Amber Reck Atwater, MD, adjunct professor of dermatology, Duke University, Durham, NC, and Nina Botto, MD, of the department of dermatology, University of California, San Francisco, in a paper published in Dermatitis. Botto also presented the Allergen of the Year at the annual meeting of the ACDS on March 6. 

PTDS, also known as toluene diamine sulfate or 2,5-diaminotoluene sulfate, is often left out of standard patch test screening series, which can lead to underdiagnosis of a contact allergy, the authors said. PTDS is similar enough to another compound, para-toluenediamine (PTD), that the authors used PTD data where PTDS data were incomplete, but the unique chemical makeup of PTDS means that the same person might not react to both. 

Data from the North American Contact Dermatitis Group for the years 2src19-2src2src and 2src21-2src22 showed PTDS positivity in 1.6% and 1.7% of approximately 3srcsrcsrc and 4srcsrcsrc patch-tested patients, respectively. 

The prevalence of PTDS is often higher among individuals with exposure to hair dyes, such as hairdressers, although cases occur in others as well, the researchers wrote. They cited two studies of hairdressers in which PTDS positivity was 15.3% and 7.9%.

What to Look For

Although reports of isolated PTDS contact allergy are rare, the presentation is similar to that of PPD allergic contact dermatitis (ACD), with eczematous conditions on the hands, hairline, periorbital area, and neck, which are common areas of hair dye contact. 

“Interestingly, with PPD-related ACD, the scalp can be spared, likely due to sebum on the scalp and the hair itself,” the authors noted. 

Options for Allergic Patients

Cross-reactions are common among the three compounds, PTDS, PTD, and PPD, the authors wrote. “PTDS- and PTD-allergic patients are not likely to be able to use PPD as a dye alternative,” they said. However, some PPD-allergic patients may be able to tolerate PTDS and/or PTD as an alternative in some circumstances, they added. 

Patients with PTDS ACD should be warned that alternative hair dyes marketed as natural or organic may still contain PTDS and PPD, so ingredients must be reviewed, the authors emphasized.

Looking ahead, PTDS meets the criteria for inclusion in a standard screening series based on prevalence in concomitantly patch-tested populations, the authors said. 

“Given the recent North American data as well as the importance of PTDS as an alternative hair dye option for some patients with PPD contact allergy, we advocate that PTDS be considered for inclusion in the next ACDS core screening series update,” they wrote.

The positivity greater than 1% prevalence supports its inclusion in standard series, and it is an important alternative hair dye option for approximately half of patients with PPD contact allergy, she told Medscape.

“We need more awareness about this allergen and that it is an alternative for about half of patients who are PPD allergic, which will allow providers to ask for extended series testing for their patients,” said Botto. “Hair dye allergy typically starts at the hairline, face and eyelids, and usually only presents on the scalp when severe,” she noted. PPD is the most common hair dye chemically used, she added.

The main strategy to treat PTDS allergy, or any contact allergy is removing the offending allergen, which means avoiding hair dye for many patients,” Botto said. “But since PPD allergy is the most common one that we see, testing those patients who are PPD allergic and still want to dye their hair with expanded allergy testing to PTDS allows about half of them to use PTDS as an alternative.” However, patients who are allergic to both PPD and PTDS need to avoid hair dye or use henna-based products, she added.

Looking ahead, more research is needed on the benefits of expanded series patch testing and quality of life outcomes for patients with contact allergy, Botto concluded.

Atwater was previously employed by Eli Lilly, but had no financial conflicts to disclose. Botto had no financial conflicts to disclose.