Patch tests with commercial hair dye products in patients with allergic contact dermatitis to para-phenylenediamine

The study evaluated the safety of 15 commercially available hair dye products in 23 patients with allergic contact dermatitis to para-phenylenediamine. Despite being advertised as "hypoallergenic" or "no para-phenylenediamine," 87.0% of patients had a positive patch test reaction to at least one product. Four products contained para-phenylenediamine, while others contained m-aminophenol and toluene-2,5-diamine sulfate. Only one product did not cause a reaction in any patient. The study concluded that dermatologists should advise patients to perform sensitivity testing before using any hair dye, regardless of its advertising claims. The study was limited by its small sample size and potential for false-positive reactions.