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Contact Allergens in "PPD-Free" Hair Dyes
Carli D Needle1, Emily C Milam1, Aryeh Korman2
1The Ronald O. Perelman Department of Dermatology, New York University Grossman School of Medicine, New York, New York, USA.
Dermatitis : Contact, Atopic, Occupational, Drug
|June 24, 2025
Summary
Many "PPD-free" hair dyes contain undeclared paraphenylenediamine (PPD), a common allergen causing allergic contact dermatitis (ACD). Testing is crucial before using any new hair dye, regardless of labeling.
Area of Science:
- Dermatology
- Cosmetic Science
- Analytical Chemistry
Background:
- Hair dyes are frequent causes of allergic contact dermatitis (ACD).
- Paraphenylenediamine (PPD) and related aromatic amines are primary hair dye allergens.
- Patients develop ACD even with "allergen-free" or "natural" hair dyes, suggesting undisclosed or cross-reactive ingredients.
Purpose of the Study:
- To investigate "PPD-free" hair dyes sold in the US for common hair dye allergens.
- To quantify the presence of specific allergens like PPD, m-aminophenol, and others.
- To identify undisclosed ingredients in hair dye formulations.
Main Methods:
- Analysis of best-selling "PPD-free" hair dyes using high-performance liquid chromatography coupled to high-resolution mass spectrometry (HPLC-HRMS).
- Detection and quantification of target hair dye allergens and ingredients.
- Comparison of detected ingredients against product ingredient lists.
Main Results:
- Seven out of 51 tested hair dye products contained undeclared compounds.
- Five products tested positive for PPD, with four explicitly labeled "PPD-free".
- PPD levels varied from trace amounts to over 2% by weight in some products.
Conclusions:
- "PPD-free" hair dye labels can be misleading, as PPD may be present.
- Dermatologists should advise patients with ACD to undergo allergy alert testing before using any new hair dye.
- Regardless of marketing claims, vigilance is needed regarding hair dye ingredients and potential allergens.
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