A recent epidemiologic survey in the UK revealed that 23% of women and 13.8% of men experience some sort of adverse reaction to a personal care product over the course of a year. Although most of these reactions may be due to subjective sensory irritation, various studies reveal that up to 10% of dermatologic patients who are patch tested are allergic to cosmetic products or their constituent ingredients. Causative products include deodorants and perfumes, skin care products, hair care products, and nail cosmetics. Allergic contact dermatitis mainly results from fragrance chemicals and preservatives. Recent work has suggested that additional fragrance chemicals may need to be tested in order to identify those patients 'missed' by the current fragrance mix; in particular, hydroxy-isohexyl-3-cyclohexene carboxaldehyde (HMPPC Lyral) has been singled out as an important sensitizing agent. The increased usage of natural fragrances and botanic extracts can also cause problems in their own right or through co-reactivity. The preservative methyldibromo glutaronitrile has also been recognized as an increasingly important sensitizer in Europe, which has led to the recent recommendation that it should be prohibited from 'leave-on' products until information on 'safe' consumer levels becomes available. Other emerging allergens include UV filters, tosylamide/formaldehyde resin, and nail acrylates. The diagnosis of cosmetic allergy should be confirmed with patch testing, including testing of 'whole' products, when necessary, and repeat open application tests can be used to confirm the relevance of reactions in cases of doubt.