Nettle rash

Most episodes of urticaria peak between 8 to 12 hours, then stop after 24 hours. 

The weals (skin marks) of urticaria are raised, and pink or red in colour. They are usually very itchy and range in size from a few millimetres to the size of a hand.

Individual weals normally fade after a few hours, but can be replaced by new ones elsewhere on the body. They may appear on just one part of the body or across a large part of it. The skin returns to normal as soon as the weal fades.

Urticaria vasculitis

Urticaria vasculitis is a rare form of this condition. The weals are tender, last more than 24 hours and leave a bruise. They need to be urgently looked at by a dermatologist (skin specialist).

Angioedema

Around half of people with chronic (persistent) urticaria and a quarter of people with acute (short-term) urticaria also get a related condition called angioedema.

Angioedema is swelling in the deeper layers of the skin, usually in the eyelids, lips and sometimes the mouth, although it can occur anywhere. Angioedema causes a burning sensation but is not usually itchy. It usually clears within a few days.

For more information, see Health A-Z: angioedema