Abstract: Numerous molecules can induce contact urticaria (CU) either involving a specific IgE dependent immune reaction or through a non-immunological mechanism. Systemic manifestations (rhinitis, conjunctivitis, bronchospasm, and anaphylaxis) sometimes occur with CU. A number of topical medicines can cause CU: chlorohexidine applied on mucus membranes, for example, can induce severe CU with anaphylaxis; iodinated povidone, alcohol and Emla® cream rarely do. Among cosmetics, those used in beauty parlors, for example paraphenylenediamine, ammonium persulfate and Crotein Q, are the most frequent cause of CU. Some cases of CU associated with the use of cosmetics containing plant proteins, such as wheat or sesame, will be described. Diagnosis of CU entails open tests and prick tests, occasionally intradermal tests. Testing must nevertheless be done with caution, first using very dilute solutions because of the risk of anaphylaxis. [Copyright &y& Elsevier]