Shoe Allergens: A Retrospective Analysis of Cross-sectional Data From the North American Contact Dermatitis Group, 2005-2018

Background Shoe contact allergy can be difficult to diagnose and manage. Objective The aim of the study was to characterize demographics, clinical characteristics, patch test results, and occupational data for the North American Contact Dermatitis Group patients with shoe contact allergy. Methods This is a retrospective study of 33,661 patients, patch tested from 2005 to 2018, with a shoe source, foot as 1 of 3 sites of dermatitis, and final primary diagnosis of allergic contact dermatitis. Results Three hundred fifty-two patients met the inclusion criteria. They were more likely to be male (odds ratio = 3.36, confidence interval = 2.71-4.17) and less likely to be older than 40 years (odds ratio = 0.49, confidence interval = 0.40-0.61) compared with others with positive patch test reactions. The most common relevant North American Contact Dermatitis Group screening allergens were potassium dichromate (29.8%), p-tert-butylphenol formaldehyde resin (20.1%), thiuram mix (13.3%), mixed dialkyl thioureas (12.6%), and carba mix (12%). A total of 29.8% (105/352) had positive patch test reactions to supplemental allergens, and 12.2% (43/352) only had reactions to supplemental allergens. Conclusions Shoe contact allergy was more common in younger and male patients. Potassium dichromate and p-tert-butylphenol formaldehyde resin were the top shoe allergens. Testing supplemental allergens, personal care products, and shoe components should be part of a comprehensive evaluation of suspected shoe contact allergy.