Introduction Contact dermatitis to cosmetics is a common problem in the general population, although its prevalence appears to be underestimated. We reviewed cases of allergic contact dermatitis to cosmetics diagnosed in our dermatology department over a 7-year period with a view to identifying the allergens responsible, the frequency of occurrence of these allergens, and the cosmetic products implicated. Methods Using the database of the skin allergy department, we undertook a search of all cases of allergic contact dermatitis to cosmetics diagnosed in our department from January 2000 through October 2007. Results In this period, patch tests were carried out on 2485 patients, of whom 740 were diagnosed with allergic contact dermatitis and the cause was cosmetics in 202 of these patients (170 women and 32 men), who accounted for 27.3% of all cases. A total of 315 positive results were found for 46 different allergens. Allergens most often responsible for contact dermatitis in a cosmetics user were methylisothiazolinone (19%), paraphenylenediamine (15.2%), and fragrance mixtures (7.8%). Acrylates were the most common allergens in cases of occupational disease. Half of the positive results were obtained with the standard battery of the Spanish Group for Research Into Dermatitis and Skin Allergies (GEIDAC). The cosmetic products most often implicated among cosmetics users were hair dyes (18.5%), gels/soaps (15.7%), and moisturizing creams (12.7%). Conclusion Most patients affected were women. Preservatives, paraphenylenediamine, and fragrances were the most frequently detected cosmetic allergens, in line with previous reports in the literature. Finally, in order to detect new cosmetic allergens, cooperation between physicians and cosmetics producers is needed.