[Trigger factors for psoriasis].

Psoriasis is often defined as a disease in which there is a genetic predisposition but environmental stimuli ("trigger factors") are also necessary for clinical expression. Various endogenous and exogenous factors can either induce or exacerbate the clinical features. Knowledge of these factors is of primary importance in clinical practice. This review focuses on the most common environmental trigger factors (infection/superantigens, injury/Köbner phenomenon, stress/neuropeptides, smoking and alcohol) and evaluates the clinical and experimental concepts to explain "environmentally" triggered psoriasis.