Factors associated with multiple contact allergies in Thai dermatitis patients: A 10-year retrospective study

Background Multiple contact allergies (MCAs) are defined as three or more positive patch test reactions to unrelated antigens. Factors associated with MCAs include female sex, older age, and certain eczema sites. Objectives To investigate the prevalence of MCAs, risk factors for their development, and patterns of allergen combinations. Methods This retrospective, case-control study was conducted on patients suspected of having allergic contact dermatitis who had been patch tested with a baseline series in the period January 2007 to December 2016. Results Of the 2178 included patients, 531 (24.4%) had MCAs. A multivariate analysis showed that a generalized distribution of dermatitis represented the highest risk factor (odds ratio [OR] 3.97), followed by a history of metal allergy (OR 3.18). The other significantly associated factors were, in order of decreasing frequency, the dermatitis sites (hands/feet, extremities, and face), age ≥25 years, and occupationally related dermatitis; their ORs were Conclusions The factors that were significantly associated with MCAs were identified. The ranking of the common contact allergens among MCA patients was comparable with that of non-MCA patients. Metal and fragrance allergens were frequently found to cause concurrent positive reactions in MCA patients.