Contact allergy to cosmetics: testing with patients' own products.

In a 2-year period, 1527 patients with contact dermatitis were investigated in the patch-test clinic. In 531 patients, allergy to cosmetics was suspected from the history and they were tested with their own cosmetic products. 40 (7.5%) (of the 531 patients) had 1 or more positive reactions, 82 (15.4%) had doubtfully positive reaction(s) and 31 (5.8%) had irritant reaction(s). Skin-care products were tested most frequently and were also found to cause most positive, doubtfully positive and irritant reactions, 80% of the patients with positive reactions to their own products had no history of contact dermatitis prior to the presenting attack, and in 92.5% of the cases, the positive reaction was considered relevant or partly relevant. In patients with a positive reaction, ingredients that could be responsible were found in 60% of the cases by testing with the European standard series and a series of common cosmetic ingredients. Fragrance mix and formaldehyde were found to be the ingredients most often responsible and were significantly more frequent in patients with positive reactions to their own products, compared to a control group of eczema patients also seen in the patch-test clinic.