Contact allergies are frequent diseases and often lead to social and economic consequences for the patients. The incidence of the clinically manifest allergic contact eczema is between 1.8 and 7 per 1,000 per year, according to the data of the Information Network of Departments of Dermatology (IVDK; http://www.ivdk.org). Contact allergies are frequently acquired at the workplace, but a sensitisation and subsequent manifest disease (elicitation) occurs even more often in the private sphere and then poses a special problem. Even if occupational exposure to the allergen is prevented, e. g. by giving up the job, a full remission is only achieved in about half of the cases due to the ubiquitous existence of the responsible allergens. Contact with substances that have a high sensitisation potential can be avoided to a great extent. Prevention can be achieved by personal protective measures, a decrease of the applied concentration of the allergen, or even restrictions concerning certain chemicals. The prerequisite for this is continuous monitoring of the frequency of sensitizations towards known allergens, as well as an understanding of the substances in use in the environment, including newly introduced chemicals, and the education of the public.