Allergies are overreactions of the immune system to normally harmless substances. Well-known examples for allergens include animal hair, dust mites or pollen. Allergic reactions can vary significantly with regard to severity and intensity: while some allergy sufferers may only sneeze when exposed to pollen, others may develop breathing difficulties or suffer an allergic shock. For the successful treatment of allergies an early and professional diagnosis including idenfication of the allergy triggers is important. About 90 % of allergies are caused by relatively well-known triggers. Contact allergies, such as those to nickel or plaster, are another significant field. Depending on the type of allergy the diagnosis is made using prick, intracutaneous or scratch tests, as well as epicutaneous and oral challenge tests, followed by the corresponding laboratory tests.