The earliest known evidence of peanut farming dates back 7,600 years. With a prevalence of roughly 1%, peanut allergy is a diagnostic and treatment challenge, but is also a very good model for studying all aspects of food allergy, including its molecular basis and pathomechanisms. Therefore, the very starting point for elucidating all these aspects is the identification of peanut allergens with subsequent clearing of their structure and their preparation as pure recombinant and/or natural allergens. This is the basis for in vitro diagnostic tests as well as the development of immunotherapeutic drugs. With regard to class I food allergy, peanut allergy affects by far the largest group of patients. In peanuts, 12 allergens have been identified and their molecular characteristics are described herein. Ara h 1, Ara h 3.01 and Ara h 3.02 (the former Ara h 4) belong to the cupin superfamily. The conglutins Ara h 2, Ara h 6 and Ara h 7, and the non-specific lipid transfer protein Ara h 9 belong to the prolamin superfamily. Ara h 5 (profilin) and Ara h 8 (Bet v 1-homologous protein) cause class II food allergies and are associated with inhalation allergy to pollen via the sequential and/or conformational similarity of molecules. Two peanut oleosins are listed as Ara h 10 and Ara h 11 and two defensins as Ara h 12 and Ara h 13 by the WHO/IUIS Allergen Nomenclature Subcommittee. The effect of the above-specified allergens has to be considered in the context of their matrix, which is influenced by processing factors and the individual's immune system.