Most people have heard about hives (officially called urticaria) because many people develop them at some point in their lives. Hives come in different shapes and sizes. Typically a single hive is a small to large, raised, itchy "wheal" of skin that lasts no longer than a day and usually clears up within a few hours. Sometimes hives appear in groups or clusters. They are usually very itchy.
Most people experience what is called acute urticaria where the hives are short lasting, of a known origin, and do not recur. However, a small percent of people have hives of unknown origin occurring frequently and are diagnosed with chronic urticaria. Urticaria is classified as chronic when it is recurrent for at least six weeks.
Causes of hives
Since hives (urticaria) can be caused by lots of different things, or in some cases a combination of things, it is often challenging to identify an exact reason for the hives. However, the following causes of hives should always be considered:
- Allergic reaction to certain types of food, such as milk, egg, wheat, soy, peanut, tree nuts, fish, and shellfish.
- Allergic reaction to certain types of medications, such as penicillin and other antibiotics, aspirin, non-steroidal anti-inflammatory drugs (such as ibuprofen) and sulfa drugs.
- Allergic reaction to insect stings from bees, wasps, yellow jackets or fire ants.
- Eating a particular food and then exercising can cause food-dependent, exercise-induced hives.
- Allergic reactions to items through occupational contacts such as natural rubber latex, flour, grains, feeds and a variety of plant and animal species.
- Physical, environmental, and behavioral factors such as stress, trauma, pressure, friction, heat, cold, water, sunlight, exercise, alcohol, and vibration.
- Underlying diseases such as thyroid disease, hepatitis, lupus (systemic lupus erythematosus) or some types of cancer; these are much less common.
- Often, especially in children, hives can occur during or after a viral illness, including the common cold.
Every diagnosis begins with a detailed medical history and exam. Questions about the nature of the reaction, where and when it occurs, and whether the hives seem to be associated with a particular substance or event are important pieces of information. You may be asked to keep a detailed diary recording outbreaks, foods eaten, drugs taken, environmental factors and activities. Questions about work are also important because many occupations can be associated with hives. Since allergy may be genetic, expect some questions about other family members who may be allergic.
Depending on your history, different skin tests or blood tests may be performed. The number of tests performed is determined after your doctor obtains your history. Occasionally for physical urticaria, tests such as an exercise study or ice cube challenge may be recommended. Rarely, we may need to perform a skin biopsy of the hive to better understand the type of reaction that is occurring in the inflamed skin.
In some people, laboratory testing to rule out a serious illness of which hives can be a symptom (such as thyroid disease, hepatitis, lupus [systemic lupus erythematosus], or some types of cancer) may be needed. Generally speaking, less than 1 to 1 ½ % of the time is an underlying serious medical condition determined to be the cause of chronic hives. After ruling out an underlying serious illness, identifying the trigger factor or source of hives is essential.
Eliminating or avoiding an identified source or trigger of the hives is the best way to treat them. In the case of chronic hives, the cause can be thought of as autoimmune rather than an external trigger. Any underlying systemic illness thought to be contributing to or causing the hives must be treated. In most cases of chronic hives, there is no cure for the underlying cause and management involves medication to prevent the symptoms while the body resolves the process on its own over time.
In most cases, non-sedating antihistamines (such as cetirizine, fexofenadine, loratadine, etc.) are prescribed as the first line of defense and can greatly reduce itching. Often, patients with hives need to take these antihistamines more frequently or in higher doses than one usually takes for other conditions such as hayfever. If symptoms persist, additional antihistamines such as H2 antagonists (ranitidine, famotidine, cimetidine, etc.) may be added or tricyclic antidepressants or leukotriene modifiers can be added. Newer medication such as omalizumab, an injectable medication can be used for chronic hives. In severe cases, an oral steroid may be prescribed, but it should be used cautiously and tapered off as soon as symptoms are under control because of the possibility of serious side effects.