Skin lesions caused by allergic contact dermatitis are an important occupational and environmental disease. Patch testing is the gold-standard procedure used to diagnose allergic contact dermatitis.The present chapter summarizes aspects of patch testing for the diagnosis of contact allergy: important working definitions, relevance of treating contact dermatitis, materials, technique, test result and interpretation, and special consideration regarding individual factors which influence the patch test outcome or necessitate special attention.Performing and interpreting patch tests requires know-how. Knowing how to perform them and the particularities of specific cases is essential to correctly interpret the results. A correct evaluation and diagnosis will significantly impact the natural history of the disease and significantly improve the quality of life of the patient.
