Physical urticaria

Types:

• dermographism - seen in 3-5% of the population
  • dermatographism - minor trauma
• pressure - eg. on buttocks or soles. The swelling may be delayed for several hours, and usually persists for 1-2 days
• temperature: - cold - due to ice; cryoglobulins eg. in lupus erythematous; immersion in water. Tolerance may be induced by taking regular cold showers. - heat - eg. hot water
• solar - due to ultraviolet exposure
• aquagenic - due to contact with water irrespective of it's temperature
• cholinergic - exercise, emotion
• delayed pressure - jogging, sitting, lying, tight clothing
• cold - swimming in cold water, cold wind
• exercise - physical exertion
• solar - sunshine
• vibratory - use of vibrating tools

Investigations:

• challenge testing with appropriate stimuli e.g. ice-cube, exercise, etc.; cryoglobulins

Many patients have a physical element to their urticaria with triggering by heat, cold, pressure, vibration, water, ultraviolet light, etc. The physical urticarias are triggered reproducibly after a specific physical stimulus is applied . Weals usually appear immediately and often last for <2 h. A few patients have delayed-pressure urticaria, which as the name implies, comes on slowly after pressure, and lasts several hours or days. The physical urticarias can be more resistant to therapy and follow a protracted course

Reference:

• (1) Powell RJ et al; British Society for Allergy and Clinical Immunology (BSACI). BSACI guidelines for the management of chronic urticaria and angio-oedema.Clin Exp Allergy. 2007 May;37(5):631-50