Hives are raised red bumps (welts) or splotches on the skin. They are a type of swelling on the surface of your skin. They happen when your body has an allergic reaction to an allergen, a substance that’s harmless to most people.


  • Airborne allergens like tree and grass pollen, mold spores and pet dander.

  • Bacterial infections, such as strep throat and urinary tract infections.

  • Food allergies to milk, peanuts and tree nuts, eggs, fish and shellfish.

  • Insect stings.

  • Medication allergies, including non-steroidal anti-inflammatory drugs (NSAIDs), codeine and blood pressure medicine, especially ACE inhibitors.

  • Quick changes in body temperature due to heat, cold or physical activity.

  • Viral infections, such as the common cold or mononucleosis.

  • Allergies to other materials, like latex or detergents.

  • Hormonal issues, like changes in your body because of pregnancy, menopause or thyroid disease.

  • Autoimmune conditions.



Hives or swelling that last for less than six weeks are considered acute, meaning they come on suddenly. Allergic reactions to certain foods or medications often cause acute hives and swelling.


When hives linger for more than six weeks, the condition is chronic. In 95% of chronic conditions, nobody knows what causes them, though it is thought to be autoimmune in nature.


Some people develop hives and swelling in specific situations. Hives might pop up when you’re in the cold, heat or sun. Some people react to vibrations or pressure, or exercise and sweating. Physical hives usually appear within an hour after exposure.


Hives look different depending on the person and the situation. They can show up anywhere on your body. Signs of hives include:

  • Red, raised welts or bumps on the skin.

  • Blanching (the center of the hive turns white when pressed).

  • Itchy skin.

  • Swelling (angioedema).


Skin tests

  • During this test, healthcare providers test different allergens on your skin.

  • If your skin turns red or swells, it means you’re allergic to that substance.

  • This type of allergy test is also called a skin prick or scratch test.

  • Skin testing is not commonly done if hives are chronic in nature.

Blood tests

  • A blood test checks for specific antibodies in your blood.

  • Your body makes antibodies to fight off allergens.

  • The process is part of your immune system but if your body makes too many, it can cause hives and swelling.


Allergy medications

  • Medicines called antihistamines block histamine’s effects on your body.

  • Antihistamines relieve itching from hives and prevent allergic reactions.

  • Some antihistamines react fast, like diphenhydramine (Benadryl).

  • Depending how severe the hives are, your healthcare provider may recommend daily over-the-counter (OTC) or prescription allergy medications, like loratadine (Claritin). fexofenadine (Allegra), cetirizine (Zyrtec) or levocetirizine (Xyzal).

Allergy shots

  • For hard-to-treat chronic hives, your healthcare provider may recommend a monthly injection of a drug called omalizumab (Xolair).

  • This medication blocks the body’s allergy antibody, immunoglobin E (IgE), from causing allergy reactions.

  • People with severe allergies can make too much IgE, leading to problems like hives and asthma.

At-home treatments

  • To relieve hives, you can take a cool bath or shower, wear loose-fitting clothing and apply cold compresses.

  • An OTC hydrocortisone cream, such as Cortizone, can relieve itching and swelling.


  • Severe allergic reactions and swelling can lead to a life-threatening condition called anaphylaxis.

  • Symptoms include hives, swelling, shortness of breath, wheezing, vomiting and low blood pressure.

  • People experiencing anaphylaxis need an immediate epinephrine injection (EpiPen®) to open a swollen airway.

Oral steroids

Corticosteroids, such as prednisone, can relieve hive symptoms that don’t respond to antihistamines.

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