What is Urticaria?
Urticaria is the medical name for hives. Hives are raised, red, itchy welts, which form on any part of the skin. Cells in the skin called mast cells release a chemical, histamine, into the skin. Histamine allows blood plasma to leak into the superficial layer of the skin and cause the swellings. Hives are relatively common and occur in about 20% of the population at some time during their lives. Each hive typically lasts less than 24 hours and often resolves in 2 to 4 hours. New lesions may develop before the old ones fade. Hives can be very small or quite large as they join together. There are multiple causes of hives, including the most common, unknown etiology (who knows?).
- Acute Urticaria (foods, drugs, infections, environmental contacts)
- Physical Urticaria (pressure, vibration, temperature, sunlight)
- Dermatographic Urticaria
- Chronic Urticaria
If hives are accompanied by dizziness, wheezing, difficulty breathing, tightness in chest, or swelling of the tongue, lips or face, seek immediate medical attention. These symptoms may be a sign of a serious (anaphylactic) reaction.
Almost every patient will notice his or her symptoms (especially itch) worsen with stress. Although stress does not directly cause hives, it can make them worse. Cholinergic hives are a special form of hives caused by stress and by overheating.
By definition the hives have been present for less than 6 weeks. It is much more likely to identify a specific cause in these patients as compared to those who have chronic urticaria lasting over 6 weeks. This type of urticaria tends to happen in younger patients and may be caused by drugs, foods, insect stings, environmental contacts (e.g., animals, pollens) and infections. Approximately 50% of these patients also have swelling affecting eyelids and lips. This is known as angioedema. If swelling involves the airway, emergency treatment is required. When caused by foods, the rash typically begins within 90 minutes of consumption. When associated with infection, the hives can begin before symptoms of illness begin or after the symptoms have resolved.
Hives can be caused by events or exposures, which irritate skin, for example: sunlight, cold or hot temperature, water, and vibration.
Solar urticaria develops when the skin is exposed to any ultraviolet light source, such as sun light or sun lamps. The reaction, characterized by redness, itching and wheals, may occur more quickly the more a person is exposed to ultraviolet light.
This type of hive develops after firm stroking of the skin or beneath tight fitting clothes. This occurs in about 5% of the general population. This happens because the mast cells in the skin release histamine easily.
By definition the episode of hives has been occurring for over 6 weeks. Unfortunately the longer a patient has had the hives the less likely we are to find the cause. About 80% of these patients’ hives are classified as idiopathic which means we cannot find the cause. It is estimated that 30-40% of these patients get the hives because their body is making an antibody that causes cells in the skin to release their histamine. This is not due to an allergy to something in the environment. Once again the rash can occur anywhere on the body and about 50% of patients have swelling of eyelids and lips. If swelling involves the airway, emergency treatment is required.
Angioedema is swelling of the tissue. Angioedema can be seen with hives and is considered part of this disorder. Superficial swelling causes the hives while deeper swelling causes angioedema. This can be disfiguring and typically affects the face, throat, and gastrointestinal tract. If angioedema occurs without hives further immunologic evaluation is necessary.
Treatment of hives involves avoiding the causative agent if identified. If hives are persistent a medical evaluation is necessary to rule out underlying causes and possible triggers. In addition, various medications are used to suppress the rash. The mainstay of treatment includes antihistamines. The main goal of treatment is to control and decrease patient discomfort from itching. At times, control of the symptoms occurs without complete resolution of the rash.
At any time if a hive does NOT resolve or leaves a stain or bruise further medical evaluation is needed.