Mechanical trauma and urticaria.

Urticarial responses in skin may be elicited in different ways, viz, stroking (dermographism), after sustained pressure (delayed pressure urticaria), and after vibration (vibratory angio-oedema). Pressure may localise lesions of chronic idiopathic urticaria. Trauma may exacerbate hereditary angio-oedema. The extent of the morbidity caused by trauma-induced urticaria among workers is unknown.