This course, delivered in one of the most advances centers of patch testing in Europe, will provide attendees with an updated view on the pathophysiologic mechanisms of contact dermatitis, both delayed and immediate reactions, the different patterns of contact dermatitis, mainly eczematous reactions but also lichenoid, pustular, erythema multiform-like, pseudolymphomatoid, granulomatous and pigmented reactions, and the main procedures (skin tests) used for their ethiologic diagnosis.