This article presents information on tools for in-vitro determination of drug allergy. Particularly the penicillins were found to give rise to allergic reactions with accompanying antibodies, which provided possibilities to intense studies of mechanisms in hapten immunity. Thus methods to identify the metabolism of the penicillins was described by several research groups and a number of determinants, the so called major and minor determinants, were serologically identified as well the kinetics for the binding of these structures to high molecular weight carriers.