Definition

Hives are small, itchy, red swollen areas on the skin. The swelling occurs alone or in groups. Most hives tend to fade within a few hours to a few days. However, some last a few weeks or longer.

Hives © Nucleus Medical Media, Inc.

Causes

Hives are often caused when the body releases a chemical called histamine. Histamine is released during an allergic reaction. Many people, though, get hives without being exposed to something they are allergic to.

Things that may cause hives are:

• Food allergies or reactions, most commonly:
  • Milk
  • Eggs
  • Nuts
  • Fish or shellfish
  • Wheat or soy
• Medicines
• Insect bites or stings
• Latex
• Pressure, cold, heat, or sun
• Stress
• Certain health problems, such as:
  • Viral infections, such as HIV infection, hepatitis, and cytomegalovirus
  • Immune system problems
  • Vasculitis (inflamed blood vessels)
  • Thyroid disease—hypothyroidism or hyperthyroidism
  • Some cancers, such as lymphoma
  • Diabetes Type 1

Risk Factors

Things that may raise the risk of hives are:

• Being exposed to an allergen—something that causes an allergic reaction
• Being exposed to something that triggered hives in the past

Symptoms

Symptoms of hives can vary from mild to severe. They may include:

• Itchiness, redness, and swelling
• Excessive swelling of the eyelids, lips, or genitals
• Burning or stinging
• Problems breathing or swallowing

Diagnosis

The doctor will ask about your symptoms and health history. A physical exam will be done. You may need to see a doctor who treats skin disorders or allergies.

Tests may be done, such as:

• Blood tests
• Skin prick test—to check for allergies
• Skin biopsy

Treatment

The goal is to find and avoid the cause of hives.

Medicines may help to ease symptoms and manage the cause. They may be applied to the skin or taken as a pill. They may include:

• Antihistamines
• Leukotriene antagonists
• Steroids
• Anti-inflammatory medicines
• Medicines to treat the immune system

Prevention

The best way to prevent hives is to avoid allergens that caused hives in the past..