Hives (Urticaria & Angioedema)
Table of Contents
- Hives facts
- What are hives (urticaria) and angioedema? What do hives look like?
- What causes hives and angioedema? Are hives contagious? Does stress cause hives?
- What are the different kinds of hives?
- What are the signs and symptoms of ordinary hives?
- What are the risk factors and causes of ordinary hives?
- What are the causes of chronic hives?
- Are there other conditions that mimic hives?
- What specialists treat hives?
- What is the treatment for hives?
- What is the prognosis of hives?
What are the causes of chronic hives?
Chronic hives (defined as lasting six weeks or more) can last from months to years. The evaluation of this condition is difficult, and allergy testing and other laboratory tests are only occasionally useful in such cases. The accurate evaluation of this condition requires the patient to give his or her physician precise information regarding their complete medical history, personal habits, and oral intake. Occasionally, it may be necessary to limit specific foods or drugs for a time to observe any affect upon the skin condition. Certain systemic diseases and infections may occasionally present in the skin as hives. If an inciting cause can be determined, then specific treatments for that condition ought to be effective, or in the case of food or drug allergy, strict avoidance would be necessary. There are additionally rare forms of chronic urticaria that are produced when the patient makes antibodies against molecules on the surface of their own mast cells. There are tests available to identify this type of hives.
Physical urticaria (for example, heat hives) is a type of chronic urticaria produced by physical stimuli. Common environmental provocations such as sunlight, water, cold, heat, exercise, and pressure occasionally induce hives. Dermographism, which literally means "skin writing," is a common cause of physical urticaria. This is an exaggerated form of what happens to anyone when their skin is scratched or rubbed; a red welt appears at the site of the scratch. In dermographism, raised, itchy red welts with adjacent flares appear wherever the skin is scratched or where belts and other articles of clothing rub against the skin, causing mast cells to leak histamine.
Another common form of physically induced hives is called cholinergic urticaria. This produces hundreds of small, itchy bumps. These occur within 15 minutes of exercise or physical exertion and are usually gone before a doctor can examine them. This form of hives happens more often in young people.