Background: Finding alternative hair dyes for individuals allergic to para-phenylenediamine (PPD) has been difficult. Newer permanent and demipermanent hair dyes that have replaced PPD with para ...

A chemical compound used in many permanent hair dyes has been named Allergen of the Year for 2025 by the American Contact Dermatitis Society (ACDS). Toluene-2,5-diamine sulfate (PTDS) is an ...