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Background The common contact allergens may change over time as the environmental exposure changes. Objectives To identify the prevalence rates and changing trends of contact allergens in Taiwan over a 40-year period. Materials & methods The patch testing results of a referral centre from 1978 to 2018 were retrospectively reviewed. The study population was divided into four groups according to 10-year intervals. The prevalence rates of contact sensitization to each agent and the clinical relevance were analysed. For patients with positive reactions to relevant allergens, the occupations and sites of dermatitis were analysed. Results From 1978 to 2018, a total of 4005 patients underwent patch testing. Successively increasing trends of positive reactions to cobalt, fragrance mix I, and para-phenylenediamine (PPD) were found. Methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) was an emerging contact allergen. Hairdressers, cosmetologists, and aromatherapists became the occupations most commonly having positive reactions in the most recent 10 years. In the first two decades, the face and neck were the most commonly affected areas. Later, hands became the most commonly affected sites. Conclusions The prevalence rates of positive reactions to cobalt, fragrance mix I, and PPD increased successively. MCI/MI was an emerging contact allergen of special concern.

Background/Objective Since 2005, there has been a significant increase in contact allergy to methylisothiazolinon (MI)/methylchloroisothiazolinone (MCI) incidences in European countries, but there has been no documented large-scale studies of such incidences in Taiwan. Methods From 1987 to 2015, a total of 2590 patients received patch testing in our Contact Dermatitis Clinic. Analyzed were patients with positive reactions to MI/MCI (Kathon CG) in patch testing and with suspected allergy to MI/MCI. Results Among the total 2590 patients, 2388 received patch testing during 1987–2005, while 202 received patch testing during 2006–2015. Because Kathon CG was not routinely patch tested for all patients from 1987 to 2005, the incidence of contact allergy to MI/MCI was thus corrected to 3/145 (2.1%) for this time period. After 2005, there were 11 patients (11/202, 5.4%) who showed positive reactions to MI/MCI. Amongst the 14 patients who showed positive reactions to MI/MCI, 12 of them were females (85.7%). The majority of the lesions was located on the hands (10 patients, 71.4%), along with the face (3 patients, 21.4%). Interestingly, 6 patients (42.9%) who showed positive reactions to MI/MCI were associated with contact allergy to essential oils, and five of them were aromatherapists. Conclusion According to our study, the incidence of MI/MCI contact allergy in a referral center in Taiwan was 5.4%. A trend of increasing incidence of contact allergy to MI/MCI was noted after 2005, which is consistent with the findings in Europe. Allergic contact dermatitis to MI/MCI should be suspected in patients who have eczema on the hands and face, especially those who are aromatherapists.

Background/objective Contact dermatitis to topical medicaments is commonly encountered in daily practice of dermatologists. The incidence and ranking of common allergens in topical medicaments may vary depending on local prescription and self-medication behavior. The objective of this study is to investigate the clinical features and common allergens of contact dermatitis to topical medicaments in Taiwan. Methods From 1978 to 2005, a total of 3717 patients had been patch tested in our Contact Dermatitis Clinic. Any case with suspected contact allergy to topical medicaments receiving patch testing was included in this study. Results During this period, a total of 608 patients were included and 603 of them completed the patch tests. Of the 603 patch-tested patients, 397 (66%) were positive for at least one antigen, and all patch tests were negative in 206 (34%). Patients with positive patch testing were characterized by younger age and location on the limbs and skin folds, while sex and atopy were not different among the two groups. A total of 1076 positive reactions to identifiable medicaments or main ingredients were recorded in 397 patients with positive patch testing. Among these positive reactions, 701/1076 counts (65%) were read as relevant. Traditional herbal medicaments (50%), antiseptics (21%), vehicle ingredients (9%), antibiotics (8%), corticosteroids (2%), anesthetics (2%), and nonsteroidal anti-inflammatory drugs (1%) were the most common sensitizers in this study, and the common concomitant allergens were fragrance (52%) and metal (20%). Conclusion The results emphasized the special cultural consideration in Taiwanese patients with contact dermatitis to topical medicaments.

Background: Correlation of several patient factors with contact sensitization to nickel, cobalt, chromate, and other metal allergens has not been reviewed in the Taiwanese population. Objectives: A retrospective analysis was performed to define the characteristics of patients with positive patch tests to metals in a tertiary referral medical centre between 1978 and 2003. Patients and Methods: Patch test data of 3559 patients at a medical centre in Taiwan from 1978 to 2003 were retrospectively analysed. Contact sensitization to metals was defined as a positive reaction to at least one of the metal substances in the patch test series. Chi-squared test, Fisher’s exact test, and multivariate logistic regression were used for statistical analysis. Results: Female patients were more likely to have contact sensitization to metal allergens except chromate or mercurochrome. Patients who reacted to chromate were more likely to be male, with an occupational correlation, older age, and a site of predilection towards the extremities. Within the first and sixth decades of age, thimerosal and chromate were the leading causes of metal contact sensitization, respectively. Nickel was the major metal sensitizer among the other age groups. Conclusions: Several patient factors were characterized related to metal sensitization in the Taiwanese population. The sources of exposure were further discussed.