Patch test characteristics of patients referred for suspected contact allergy of the feet--retrospective 10-year cross-sectional study of the IVDK data.

BACKGROUND: The warm und humid environment, friction and occlusion within shoes make the feet to a favorable body site to acquire allergic contact dermatitis.
OBJECTIVES: To evaluate and compare patch test results in patients with suspected contact allergy of the feet with the results in those with concomitant involvement of the feet/legs, feet/hands, and all others tested (excluding secondary involvement of the feet in 'others'), with regard to specific patterns of clinical data and patch test results.
METHODS: For the present cross-sectional study, data were collected by the 59 participating centres of the Information Network of Departments of Dermatology in Germany, Austria, and Switzerland, including 102 209 patients patch-tested between January 2001 and December 2010.
RESULTS: Allergens that were significantly over-represented in the tested 2671 foot patients included potassium dichromate, colophonium, and p-tert-butylphenol-formaldehyde resin. Among materials brought in by the patients, shoe pieces (27.5%), topical medications/pharmaceutical products (24.4%) and cosmetics (16.8%) played a major role. The final diagnoses of vesicular and hyperkeratotic dermatitis, as well as psoriasis, were significantly more common among foot patients.
CONCLUSIONS: Chromium compounds and adhesives were the most common causes of allergic contact dermatitis among our foot patients. Psoriasis should be considered, particularly when the hands are concomitantly affected.