Urticaria (commonly called “hives”) is the term for a group of disorders affecting adults or children. The appearance is of a pattern of swelling of the skin surface, anywhere on the body, culminating in pink bumps. Hives are usually itchy and cause swelling of the skin that is usually generalized (doesn’t occur on any one part of the body) and symmetrical (doesn’t appear only on one side of the body). There are usually no blisters and each lesion can vary from a small lesion/bump to large involved areas. About 20% of individuals experience urticaria at some point during their lifetime. It can be transient and is usually associated with itching, but can be felt as a stinging or a burning sensation. Hives can last 12-24 hours or can be chronic.
The cause of the hive is usually unknown, although drugs are common culprits. Food including food additives and supplements can also be the cause of the hive. Other causes may be infection (e.g., strep or dental infections or viruses) or physical stimuli (e.g., pressure, cold, heat, sun, exercise, stress, water).
The most common foods that cause hives are shellfish, chocolate, nuts and peanuts, fish, tomatoes, eggs, fresh berries, and milk. Fresh foods cause hives more often than cooked foods. Food additives and preservatives may also be responsible. The best treatment for hives is to find the cause and then eliminate it. Unfortunately, this is not always an easy task: extensively questioning patients and performing blood testing is only successful in finding the cause of the hives in about half of the cases.
The skin swelling is due to the release of a histamine chemical found in the skin released from a type of cell called a “mast cell”; this causes the swelling. The affected skin is usually itchy and each wheal (bump) may last minutes to hours. Treatment options vary but usually include antihistamines and systemic therapies.
Angioedema is a rare form of hives that involves deeper tissues, causing swelling of the lips, mouth, respiratory or GI tracts. Angioedema can be life-threatening if it involves the lungs because it can lead to rapid throat swelling. The most serious type of allergic reaction is called anaphylaxis, threatening a rapid throat swelling associated with low blood pressure that can be quite dangerous.