Urticaria

From ArticleWorld

Urticaria is also known as hives. It is a common allergic reaction that can be localized or generalized and involves the presence of itchy, raised, red welts. It is sometimes called a nettle rash.

Pathophysiology

Urticaria can be caused by allergic and non-allergic means. Regardless of the cause, the rash is due to the onset of inflammation in the skin that causes leakage of the small blood vessels of the skin and the release of histamine from mast cells in the tissues. Histamine release causes the welt-like lesions, some of the redness and the intense itchiness of this rash.

Allergic urticaria is caused by a medication, such as an antibiotic, or other medications to which a person has a substantial allergy. Foods, such as shellfish can also trigger this reaction. Some dyes used in foods are allergenic and can cause hives. In some cases, contact with an allergen can cause localized hives, which then spreads to affect the whole body. Non-allergic urticaria is actually quite common. It is usually caused by stress, which releases neuropeptides that signal an allergic response.

Urticaria can be “acute” and occurs only a few minutes after contact with the allergen. Food and drug allergies can act like this and can persist for several hours or even several weeks. “Chronic urticaria” lasts for six weeks or more and is due to continued exposure to an allergen or to stress-induced non-allergic hives that occur in the presence of continued stress.

Physical urticaria is rare and is due to contact with a variety of things. Exposure to water, body heat, sunlight, external heat, vibration, scratching, pressure or cold can cause what begins as localized itching and sometimes spreads to involve the entire body.

Treatments

The easiest treatment for urticaria is the use of an antihistamine such as diphenhydramine. Not only will it reduce itching, it will often reverse the process by reducing sensitivity to itching. Reducing the itching often helps limit the histamine release in this disorder. In some cases, the use of histamine-2 blockers, generally used to treat stomach acid disorders, will also help.

In other cases, especially when stress appears to be a factor, using medications, such as benzodiazepines, helps relieve the stress and anxiety that precipitates the disorder and also keeps it from resolving. Rarely, oral corticosteroids are used to blunt the immune response, although it is not generally recommended alone or for long periods of time.