What are hives?
Hives, also known as urticaria, involve an itching sensation and swollen, red marks. The itching may be mild to severe, depending on the case. Hives are due to an increase in body temperature with sweating, exercise, hot showers, and/or anxiety. Try not to scratch, drink alcoholic beverages, exercise, and get emotionally stressed, as these may worsen the itching.
Symptoms of hives can last for different amounts of time. There are 2 types of hives:
- Acute urticaria: hives that last six weeks or less
- Chronic urticaria: hives that last or recur for more than six weeks
In general, the causes of acute and chronic hives vary.
What causes hives and how long do hives last?
Acute hives last six weeks or less and are generally caused by one of the following:
- Foods such as peanuts, eggs, nuts and shellfish
- Medications such as aspirin and antibiotics (especially penicillin and sulfa)
- Stings or bites
- Blood transfusions
- Infections including a cold, urinary tract infection, strep throat, infectious mononucleosis and hepatitis, among others
Generally, the hives go away when the cause is avoided, removed or treated.
Chronic hives last for more than six weeks. The cause of chronic hives is unknown although the immune system is often involved. In other cases, chronic hives may be associated with thyroid disease or other hormonal imbalances. In most cases, chronic hives gradually disappears. “Physical urticaria,” a type of chronic hives in which hives can have one or more physical cause may include:
- Rubbing or scratching. The most common reason for chronic hives, these physical hives appear in the area of rubbing or scratching for less than an hour.
- Change in temperature. Hives can be caused by heat or cold, usually by exposure to low temperature followed by re-warming. This can be severe if there is a general body cooling, for example after jumping into a swimming pool.
- Constant pressure. Hives can also come in the form of red swelling caused by constrictive clothing such as belts. In some occupations they occur in parts of the body under constant pressure, such as hands in carpenters.
- Sun exposure. Hives may occur within a few minutes after exposure to the sun.
- Inflammation of the blood vessels, called vasculitis, can also cause hives. These hives are less itchy and more painful, and may leave a bruise on the skin.
How are the causes of hives identified?
Sometimes it is obvious – a person eats peanuts or shrimp, and then develops hives within a short time. In some cases, the cause cannot be identified. If the hives involve swelling of the tongue or trouble breathing, immediately go to the emergency room to be evaluated.
If a food allergy is suspected, it can be extremely helpful to jot down a diary of foods eaten before the hives started.
Chronic hives should be evaluated by an allergist. The allergy specialist will take your detailed medical history, including exposures from your work and home environment, and current and recent medications. The allergist will examine you for possible causes of hives with a skin, blood, or urine test.
The exact cause of chronic hives can be identified in about 20% of cases, although research is still being done to identify more causes and more effective treatments for hives.
What is the treatment for hives?
Hives, in most cases, are treated with antihistamines. They are effective, long-lasting and have minimal side effects. Severe cases may require temporary treatment with prednisone, a similar corticosteroid medication or immune modulator.
If the rash involves swelling of the tongue or lips, or you have trouble breathing, an epinephrine self-injector will be prescribed to carry with you at all times.
If the cause of hives can be identified, the best treatment is to avoid or eliminate it. For example:
- Foods – If a problem with a specific food is strongly suspected, you should not eat that food. Read packaged food labels and question restaurant staff about ingredients in your dish.
- Rubbing or scratching – Avoid harsh soaps and tight clothing. Frequent bathing may increase the problem of dry skin, which leads to scratching, further aggravating the condition.
- Constant pressure – Loose-fitting clothing will help relieve hives caused by pressure.
- Change in temperature – If your hives are caused by cold, you should not swim alone. If you get severe cases, you should not swim at all. Try avoiding exposure to cold, and wear warm clothing to avoid getting hives.
- Sun exposure – Wear protective clothing and apply sun block when outdoors.
- Medications – If a specific medication gives you problems, stop taking it and notify your doctor and pharmacist.