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 some 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 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 methyldibromoglutaronitrile 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.

Fragrance ingredients are the most frequent cause of cosmetic allergy, accounting for up to 30-45% of allergic reactions to cosmetics in eczema patients. As well as being found in products marketed to provide a scent they are also incorporated into the majority of other skin care products. Fragrance ingredients can cause dermatitis at the sites of application and also volatile or photosensitive patterns of contact dermatitis, but may involve other sites by direct transfer or even connubial contact.

Managing patients with proven fragrance allergy often proves extremely difficult. Advising patients to use products labeled as 'fragrance free' will not necessary avoid all contact with fragrance materials due to a discrepancy in the accepted definition of the term. Fragrance is defined as any substance, natural or synthetic, used solely to impart an odor to a cosmetic product. However, if a fragrance material has more than one function (e.g. preservative or emollient) it could legally still be included in a fragrance-free product.

Although these masking fragrances are uncommon sensitizers, fragrance-allergic patients should avoid them wherever possible. These substances include benzyl alcohol, benzaldehyde, and cyclopentadecanolamide. Consumers may also be unaware that rose oil, sandalwood oil, and cedarwood oil are all fragrances and that other essential oils, flower plant extracts, and flavorings are also usually fragrances. Therefore, it is important to acknowledge that natural fragrances and botanical extracts may also cause problems for the fragrance-allergic individual.

Though further research is needed, a recent study has found that a common group of chemicals used to preserve deodorants have been detected in breast-cancer tissue. Researchers at the University of Reading in England found traces of these chemicals, called parabens, in 18 out of 20 samples, suggesting that they may be absorbed by the body after they are applied to the skin. By reading the ingredients of the products you purchase you can become educated on what they contain and be able to reduce unwanted substances.