Author: Dr Roy Palmer
The rash of urticaria is itchy and often widespread. Each hive has the appearance of nettle rash and lasts minutes or up to 24 hours. There are several different types of urticaria.
The acute form is often due to allergy. After exposure to an allergen, the allergic person develops the rash, usually very quickly (eg. within 5 or 10 minutes).
In the chronic form (‘chronic spontaneous urticaria’) patients develop the hives continuously, without exposure to an allergen. The itch can be debilitating. The first line of treatment is antihistamines. If they are ineffective then other oral treatments are available. Recently an injected drug called omalizumab has become available; one injection is effective for a few weeks, but each injection costs about £800.
Sometimes physical factors, such as pressure on the skin or scratching the skin, encourage the hives to form. Some patients only develop the hives after specific physical factors, such as scratching (this is called dermographism).
The British Association of Dermatologists have a good patient information leaflet on urticaria;