Definition

Hives are small, itchy, red swellings on the skin. The swelling occurs singularly or in clusters. Hives tend to fade after a few hours, but new ones can appear. Most cases go away within a few days. But, some last a few weeks or longer.

Hives

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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.

While the cause is unknown in some cases, these factors may cause hives:

• Foods]]> , most commonly:
  • Eggs
  • Shellfish
  • Nuts
  • Chocolate
  • Fish
  • Tomatoes
  • Fresh berries
  • Milk
• Medications
• Reaction to ]]>allergy shots]]> (desensitization shots)
• Infections
• ]]>Insect bites or stings]]>
• ]]>Latex]]>
• Pressure
• Cold or heat
• Sunlight
• Thyroid disease ( ]]>hypothyroidism]]> , ]]>hyperthyroidism]]> )
• Pollen
• Stress
• Vasculitis (inflammation of the blood vessels)

Risk Factors

A risk factor is something that increases your chance of getting hives. Tell your doctor if you have any of these:

• Exposure to an allergen (something that causes an allergic reaction)
• Exposure to an allergen that triggered hives in the past

Symptoms

Symptoms of hives can vary from mild to severe:

• Itchiness
• Redness
• Swelling
• Excessive swelling of the eyelids, lips, or genitals
• Burning
• Stinging
• Difficulty breathing or swallowing—Call 911 if you are having these symptoms

Diagnosis

The doctor will ask about your symptoms and medical history, and perform a physical exam. You may need to see a doctor who specializes in skin disorders (dermatologist) or allergies (allergist). The following tests will be done:

• Skin prick test]]> —a tiny bit of an allergen is placed in your skin with a needle to see if the area becomes raised or irritated
• ]]>Skin biopsy]]> —a small portion of abnormal skin is removed
• ]]>X-ray]]> —a test that uses radiation to take a picture of structures inside the body, especially bones
• Blood tests

Treatment

The best way to treat hives is to find and then avoid the cause.

If the cause can't be found, there are medications to treat hives:

• • Diphenhydramine]]> (eg, Aler-Cap, Benadryl Allergy)
  • ]]>Hydroxyzine]]> (Vistaril)
  • ]]>Cyproheptadine]]> (no brand name)
  • ]]>Fexofenadine]]> (Allegra)
  • ]]>Loratadine]]> (Claritin)
  • ]]>Acrivastine]]> (Semprex)
  • ]]>Cetirizine]]> (Zyrtec)
  • ]]>Doxepin]]> (Prudoxin, Sinequan, Zonalon)
  • ]]>Levocetirizine]]> (Xyzal)
• H2 blocking medications such as:
  • ]]>Cimetidine]]> (Tagamet HB)
  • ]]>Ranitidine]]> (Zantac)
  • ]]>Famotidine]]> (Pepcid)
• Anti-inflammatory medications
• Steroid skin creams
• Oral steroid medications ( ]]>prednisone]]> ) for hives resistant to other treatments
• Ultraviolet light therapy
• Prescription ]]>epinephrine]]> (adrenalin) injections for cases when swelling affects the airways

Prevention

The best way to prevent hives is to avoid allergen that caused you to get hives in the past.