What Causes Hives?
There are several types of hives, including:
Acute urticaria. These are hives that last less than 6 weeks. The most common causes are foods, medications, and infections. Insect bites and diseases may also be responsible.
The most common foods that cause hives are nuts, chocolate, fish, tomatoes, eggs, fresh berries, and milk. Fresh foods cause hives more often than cooked foods. Certain food additives and preservatives may also be to blame.
Drugs that can cause hives include aspirin and other nonsteroidal anti-inflammatory medications such as ibuprofen, high blood pressure drugs (especially ACE inhibitors), or painkillers such as codeine.
Chronic urticaria. These are hives that last more than 6 weeks. The cause is usually harder to identify than those causing acute urticaria. For most people with chronic urticaria, the cause is impossible to find. In some cases, though, the cause may be thyroid disease, hepatitis, infection, or cancer.
Physical urticaria. These hives are caused by something that stimulates the skin -- for example, cold, heat, sun exposure, vibration, pressure, sweating, or exercise. The hives usually occur right where the skin was stimulated and rarely appear elsewhere. Most of the hives appear within 1 hour.
Dermatographism. This is a common form of physical urticaria where hives form after firmly stroking or scratching the skin. These hives can also occur along with other forms of urticaria.
The Link to Contact Dermatitis
Contact dermatitis is a painful or itchy rash you get after your skin touches something you're allergic to (allergic contact dermatitis) or that's otherwise irritating to your skin (irritant contact dermatitis). It's not the same as hives. But sometimes people with contact dermatitis also get hives after they come into contact with an allergen.
How Are Hives Diagnosed?
Your doctor will need to ask many questions in an attempt to find the possible cause of hives. Since there are no specific tests for hives -- or the associated swelling of angioedema -- testing will depend on your medical history and a thorough exam by your doctor.
Your doctor may do skin tests to find out what you're allergic to. Or they may test your blood to see if you have an illness.
How Are Hives Treated?
The best treatment for hives is to find and remove the trigger, but this is not an easy task. Antihistamines are usually prescribed by your doctor to provide relief from symptoms. Antihistamines work best if taken on a regular schedule to prevent hives from forming in the first place.
Chronic hives may be treated with antihistamines or a combination of medications. When antihistamines don't provide relief, oral steroids may be prescribed. A biologic drug, omalizumab (Xolair), is also approved to treat chronic hives in people at least 12 years old.
How Can Hives Be Managed?
While you're waiting for hives and swelling to disappear, here are some tips:
- Apply cool compresses or wet cloths to the affected areas.
- Try to work and sleep in a cool room.
- Wear loose-fitting lightweight clothes.
When Should I Call the Doctor About Hives?
If you have hives with any of the following symptoms, contact your doctor right away:
- Difficulty breathing
- Tightness in the chest
- Swelling of the tongue, lips, or face