Hives, An Allergic Reaction

Hives: An Allergic Reaction

Urticaria, also known as hives, is an outbreak of pale red bumps or welts on the skin that appear suddenly. The swelling that often comes with hives is called angioedema.

Allergic reactions, chemicals in certain foods, insect stings, sunlight, and medications can cause hives. It's often impossible to find out exactly why hives have formed.

What Causes Hives?

There are several types of hives, including:

1. 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.

2. 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. Chronic urticaria can also affect organs such as the lungs, muscles, and gastrointestinal tract. Symptoms include shortness of breath, muscle soreness, vomiting, and diarrhea.

3. 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.