Urticaria, commonly known as hives, usually strikes suddenly. First the skin itches, then it erupts into red welts. It can range in size and appear anywhere on the body. Approxi¬mately 25% of the U.S. population will experience an episode of hives at least once in their lives.
Acute Urticaria is a hives lasting less than 6 weeks is the common form. These hives usually go away spontaneously. In adults, reactions to medicines are a common cause while in children; foods or viral infections can trigger acute hives.
Chronic Urticaria is hives lasting more than 6 weeks. It occurs anywhere and almost daily for months to years. These hives also will eventually disappear on their own with or without treatments. For 50% of these patients, the hives will clear in 3 to 12 months; 40% will clear in one to five years. The rest of the patient may experience hives for many years. 40% of patients with chronic hives will have at least one more episode of hives in their lifetime.
Angioedema is serious form of urticaria where there is a swelling of the deeper layers of the skin and most often occurs in soft tissue such as the eyelids, lips, tongue, larynx, hands or genitals. Hives and angioedema may appear together or separately on the body. Most of the time, the triggers for urticaria and Angioedema are the same.
Medications known to cause hives or Angioedema include aspirin and other non-¬steroidal anti-inflammatory drugs (NSAID5) such as ibuprofen, high blood pressure medicines known as ACE-inhibitors, or pain-killers containing codeine or codeine-like drugs. All drug-induced hives occur within minutes to an hour of taking the drug but in some case it might be after few days.
Children and sometime adults can also develop hives after eating certain foods and food additives, including nuts, eggs, shellfish, soy, wheat or milk—the culprits in more than 90% of proven food-induced hives.
Physical urticaria is hives resulting from an outside source: rubbing of the skin, cold, heat, physical exertion or exercise, pressure or direct exposure to sunlight. Patients with chronic urticaria often report that at least one of these triggers induces their hives.
One can identify Urticaria triggers by detailed history and maintaining a food diary. In some cases by blood, stool & urine test. Skin tests may provide useful information in some cases e.g. food & animals allergy. Patch testing is sometime done.
In the urticaria-prone person, above triggers cause the body to release chemical called histamine; thus attacks of urticaria can be temporarily relieved by antihistamine. In some case cortisone and rarely specifically for Angioedema, injections of epinephrine may be prescribed. Other drugs may be required for specific types of urticaria.
Patients with solar urticaria should wear protective clothing and apply sunscreen lotions when outdoors. Loose-fitting clothing will help relieve pressure urticaria. Avoid harsh soaps and frequent bathing which can cause itching and scratching that can aggravate urticaria. Vigorous toweling after a bath may precipitate hives and should be avoided.
Best treatment is avoidance of the substance that triggers urticaria if identified. In adult and especially in children if a specific food is suspected, it should be confirmed by allergy testing and then avoided.