The prevalence of contact allergy differed between population-based and clinic-based data

Objective Epidemiologic evidence on contact allergy (CA) largely relies on clinical studies. However, the effects of the selection process until consultation as patient are largely unclear. Study design and setting Prevalences of contact allergy to important allergens estimated from the population-based nested case-control study "KORA Allergy Study" in Augsburg, Germany (a subsample from the third MONICA survey in 1997/1998, n=1141), were compared with proportions found in the Department of Dermatology of the Augsburg Municipal Hospital in patients of similar age patch tested between 1997 and 2000 (n=555). Prevalences were standardized for sex, age, and atopic dermatitis as potential confounders. Results Among the 25 substances tested, the fragrance mix (MONICA, estimated from the KORA Allergy Study: 11.4%, hospital: 12.9%) and nickel (MONICA: 9.9%, hospital: 12.9%) were the most common allergens. Larger differences between prevalences were noted particularly with ingredients of topicals used to treat varicose ulcers - a speciality of the Augsburg department, which is also reflected by comparing the department with the whole Information Network of (n =40) Departments of Dermatology (IVDK). Conclusion This locally matched comparison illustrates the differential effect of selection until presentation in dermatological departments.