TOPLINE

Among patients who had patch testing for paraphenylenediamine (PPD), 4.3% tested positive, and many products marketed as "PPD-free" still contained closely related compounds capable of triggering similar reactions. On follow-up, 77% of surveyed patients reported complete or near-complete remission after avoiding PPD products.

METHODOLOGY

• Researchers performed a retrospective review of patch test outcomes from January 2018 to January 2025 to describe the clinical picture, cross-reactivity, and postdiagnosis outcomes among patients with PPD allergy.
• A total of 1306 patients underwent patch testing using a commercial allergen panel; PPD was tested at 1% in a petrolatum base within the baseline panel, with an additional hairdressing series applied based on clinical suspicion.
• Information extracted from electronic records included allergy history, occupation, a probable trigger, and how long symptoms had persisted. A telephone questionnaire gathered information that included symptom improvement, success in avoiding the trigger, and occupational impact.
• A structured web search (October 2025) checked the leading 50 hits per search term to find "PPD-free" dyes and eyebrow/eyelash tints sold in the UK; their listed ingredients were then cross-referenced against PPD, para-toluenediamine, aminophenols, and related compounds.

TAKEAWAY

• Overall, 56 patients (4.3%) had a positive PPD test; the mean age at diagnosis was 49 years, and 82% of the patients were women. Hair dye was the leading exposure, reported by 43 patients (77%), while eight patients (14%) — all hairdressers or hairdressing students — had occupational exposure.
• Patients had a mean symptom duration of 4.9 years before being diagnosed. Clinicians documented moderate or severe disease in 54 patients (96%), with eczematous dermatitis the most frequent presentation (n = 51; 91%).
• Among 37 patients tested for para-toluenediamine in addition to PPD, roughly a quarter (27%) had a positive reaction to para-toluenediamine. Of the 31 patients (55%) reached by telephone, 24 (77%) reported complete or near-complete remission after avoiding PPD-containing products, and all five patients with occupational exposure had changed careers or left work.
• Of seven "PPD-free" permanent dyes, only one lacked PPD, para-toluenediamine, aminophenols, and derivatives. Of three "PPD-free" brow/lash tints, two still contained para-toluenediamine and aminophenols; the third prompted a UK product safety report for misleadingly marketing a para-toluenediamine-containing product as "PPD-free."

IN PRACTICE

"Improved regulatory oversight and mandatory disclosure of all aromatic-amine derivatives on product labelling are required to protect consumers and support clinicians in advising patients," the authors wrote.

"Broader advocacy for clearer labelling and inclusion of aromatic-amine derivatives in EU and UK cosmetic safety databases is warranted. Development of validated patient- education materials and occupational-screening protocols could further reduce disease burden," they added.

SOURCE

Zara Ali, with the University Hospital Southampton, Southampton, England, was the corresponding author of the study, which was published online on September 22 in Contact Dermatitis.

LIMITATIONS

The study was limited by its retrospective nature, dependence on historical records, and incomplete patch testing that did not cover every potentially cross-reactive allergen. The product review was also limited to ingredient data available on brand and retailer websites, which may not reflect proprietary formulation details.

DISCLOSURES

No specific funding was reported. The authors reported having no relevant conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.