What are hives?

Hives (urticaria) are red, itchy, raised bumps on the skin. They often last less than 12 hours in one area of the skin.

What causes hives?

Hives may last for a short or long time. If hives last for a short time or come with other symptoms, the cause could be an allergic reaction from eating certain foods or taking certain medicines. Or they could be from a viral infection. In many cases, hives can occur without a specific trigger. When hives come and go long-term (lasting weeks, months, or years), the cause usually isn’t known.

Hives can be part of an allergic reaction to foods such as:

• Nuts

• Peanuts

• Eggs

• Fish

• Shellfish

• Milk

• Wheat

• Soy

But any food allergy could cause hives.

You may also get hives from these medicines:

• NSAIDs (nonsteroidal anti-inflammatory drugs), such as ibuprofen or naproxen

• Antibiotics, especially penicillin and related antibiotics in the same class

• Medicines for seizures and epilepsy

• Chemotherapy medicines

• Medicines for treating cancer, such as monoclonal antibodies

Other types of hives include:

• Dermatographism. These are hives caused by scratching or putting pressure on the skin.

• Cold-induced hives. These are caused by exposure to cold air or water.

• Solar hives. These are rare. They are caused by exposure to sunlight or other light.

• Exercise-induced hives. These are brought on by physical activity and often affect the neck area.

• Chronic urticaria. These are hives that keep coming back, with no known cause. This is the most common form of frequent hives.

You can also develop hives from stress, certain infections, animal dander, materials such as latex, and insect stings. They can also be a sign of a more serious health problem, such as liver disease.

What are the symptoms of hives?

Hives appear on the skin as red, itchy, raised bumps. They can vary in size and may come and go. They can affect most of the body or just a small area. Each hive usually lasts less than 24 hours and then goes away without a trace. You can continue to develop new hives as old ones go away.

How are hives diagnosed?

Your healthcare provider will ask about your health history and do a physical exam. A provider can often diagnose hives by looking at your skin if you have them at your visit. The provider will also ask questions about your symptoms. You may not have active hives on your skin when you see your healthcare provider. Bringing photos of your rash to the appointment can be helpful. Other tests may be needed to figure out what may be causing the hives. You may have:

• Allergy testing. This includes blood tests and skin tests. These tests are done only if an allergy seems to be causing your hives.

• Biopsy. Your healthcare provider may take a piece of skin and have it looked at under a microscope. This is often not needed unless your healthcare provider is not sure if you have hives or something else.

How are hives treated? 

Hives may go away without treatment, especially if they are caused by an allergic reaction. If you have an allergic trigger, staying away from the food, medicine, or other trigger can ease your symptoms.

If your symptoms last for some time or keep coming back, these treatments may help:

• Antihistamines. These medicines can ease itching and keep the hives from appearing.

• Other medicines. Steroids may help if antihistamines don’t work. But these are used only for short periods of time. They are not advised for long-term use. In severe cases, an injectable medicine called omalizumab may be used.

What are possible complications of hives?

A possible complication of hives is angioedema. This is swelling in the deeper layers of skin. It can happen with or without hives. It’s most common on the hands, feet, lips, tongue, and eyes.

Angioedema is serious. It may need to be treated right away. This is especially true if you have swelling of the tongue, lips, and throat. You may feel as if your throat is closing up, making it hard to breathe. This is a medical emergency. Call 911. Get help right away.

Key points about hives

• Hives are red, itchy, raised bumps that appear on the skin. They often last less than 24 hours in one area of skin.

• They are sometimes caused by an allergic reaction to certain foods or medicines.

• Many times, the cause of hives is unknown. If an allergy is suspected, an allergy test might help figure out what is causing hives.

• Antihistamines and other medicines can ease symptoms.

• A possible complication of hives is swelling in the deeper layers of skin (angioedema). This can be serious and requires medical care right away.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

• Know the reason for your visit and what you want to happen.

• Before your visit, write down questions you want answered.

• Bring someone with you to help you ask questions and remember what your provider tells you.

• At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

• Know why a new medicine or treatment is prescribed and how it will help you. Also know what the side effects are.

• Ask if your condition can be treated in other ways.

• Know why a test or procedure is recommended and what the results could mean.

• Know what to expect if you do not take the medicine or have the test or procedure.

• If you have a follow-up appointment, write down the date, time, and purpose for that visit.

• Know how you can contact your provider if you have questions.