Hives or Urticaria: Allergy Clinic
Why do people get hives?
About 20 percent of people will have hives sometime during their lives. Hives lasting longer than 6 weeks are called “chronic urticaria”. Most of the time the cause of chronic urticaria is unknown.
What causes hives and how are they diagnosed?
Hives or urticaria is swelling of the skin caused by the release of chemicals, such as histamine, from mast cells. Hives happen in response to a range of triggers including:
• Non-allergic:
o Post-viral
o Physical (heat, cold, touch, exercise, vibration, sun exposure)
o Certain health conditions (e.g. thyroid disease)
o Stress
• Allergic:
o Foods
o Medicines
o Insect stings
o Contact allergy (such as pets or grass)
Hives are raised, swollen welts which are very itchy and vary in size. They can appear on certain parts of the body or cover the whole body. They do not stay in the same place and may appear in other places, changing shape and size. They can last for 2-4 hours or for many weeks.
Hives are diagnosed based on medical history and physical exam. Families often label rashes as "hives" even though the rash does not appear hive-like. Because hives tend to change quickly, it is helpful to take a picture of the hives and bring it to the doctor’s office.
Evaluation of hives during a clinic visit may include blood tests or other testing of possible causes.
How are hives treated?
Avoidance is the best treatment for hives though this is not always possible especially with non-allergic hives. Antihistamines are the preferred treatment for hives.
Sedating antihistamines (such as diphenhydramine) are used for acute treatment, while non-sedating antihistamines (such as loratadine or cetirizine) may be used daily especially with non-allergic urticarias.
With chronic urticaria (hives lasting greater more than 6 weeks), other medicines may be added when needed. These medicines may include:
• Doubling of non-sedating antihistamines (morning and evening doses)
• H-2 antagonists (such as ranitidine or Zantac®)
• Leukotriene modifier (such as Singulair®)
Other medicines may be added for hives that do not respond to the above medicines. An outbreak of severe hives may need epinephrine.
Planning and Care
Finding out the cause of hives is not always easy and in some cases, the cause of hives may not be found.
It is helpful to have an up-to-date history of exposures:
• Do you or your child have food allergies? Did you or your child have a food allergy exposure? If so, follow the food allergy action plan.
• Were you or your child out in cold air (physical urticaria)?
• Were you or your child stung by a bee while outdoors?
• Did you or your child get a new medicine at home or a nonsteroidal anti-inflammatory medicine (like ibuprofen)?
• Are you or your child getting over an illness?
If there is an outbreak of hives, give Benadryl® or diphenhydramine and call the doctor’s office. If there are breathing problems call 911, and give epinephrine if you have it.
The best way to manage hives is by staying away from the foods, medicines, stinging insects, or other allergens that cause you or your child’s hives.
For more information about hives you may visit this website:
http://www.aaaai.org
The information provided should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Any duplication or distribution of the information contained herein is strictly prohibited.
Last Updated: 04/24/2012
Copyright © 04/24/2012 University of Wisconsin Hospitals and Clinics Authority. All rights reserved. Produced by the Department of Nursing. HF#7325
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