Contact allergy to preservatives in Taiwan between 1996 and 2015

Background: Preservatives are widely used in personal and industrial products. Frequent and sustained exposure to preservatives can cause contact allergy. Objective: We investigated the prevalence of contact allergic reactions to common preservatives in Taiwan over a 20-year period. Methods: A retrospective analysis was conducted among patients with allergic contact dermatitis who underwent patch testing at our clinic between 1996 and 2015. Patients who showed positive reactions to preservatives were enrolled. The location of the reaction, likely source of the allergen, and patient occupation, sex, and age were recorded. Thirteen common preservatives, including methylchloroisothiazolinone/methylisothiazolinone (MCI/MI), MI, formaldehyde (FA), paraben mix, and quaternium-15, were investigated. Results: Of 757 enrolled patients, 151 showed at least one positive reaction to preservatives. Allergy to MCI/MI (12.5%), the most frequent allergen in the standard series, showed a steeply increasing trend over time. FA (4.8%) and paraben mix (2.1%) were the next common allergens. Cosmetic products were the most common source of exposure (63.6%), while hairdressers and massage therapists were most commonly associated with occupational contact dermatitis. A sharp increase of sensitivity to MCI/MI was observed after 2006 and that of allergy to MI after 2013. Conclusions: In Taiwan, the prevalence of contact allergy to MCI/MI, MI, and parabens has increased in recent years. Individuals who are frequently exposed to cosmetic products should consider precautions against sensitization.