Hives

DEFINITION

Itchy swollen patches or bumps that appear suddenly
Location, size, and shape of patches change rapidly and repeatedly, with any one patch lasting from several minutes to several hours
Size of patches varies from a 1/2 inch to several inches across
In Caucasians, hives appear pink or red in color, with a central area of paleness

General Information

The medical term for hives is "urticaria".
Hives are sometimes an allergic skin reaction to something that the individual has eaten, touched, or in some other manner been exposed to.
Hives usually come and go for several days to a week. Sometimes they can reappear weeks or months later. Some individuals have "chronic urticaria," which means that the rash can be intermittently present for months.

Definitions

Anaphylaxis: A life-threatening type of allergic reaction.
Localized Hives: Hives on one area of the body only. Localized hives are usually due to skin contact with plants, pollen, food, a chemical, or pet saliva. Localized hives usually resolve in less than 4 hours.
Widespread Hives: Hives on multiple (2 or more) areas of the body. Widespread hives can be an allergic reaction to a food, cosmetic product, drug, insect bite, or other substance. Sometimes widespread hives show up after a viral infection. Often the cause is not found.

See More Appropriate Topic (instead of this one) If

Rash doesn't look like hives, see RASHES WIDESPREAD AND CAUSE UNKNOWN
It's probably mosquito bites, see INSECT BITES

WHEN TO CALL YOUR DOCTOR

Call 911 Now (you may need an ambulance) If

Difficult to awaken or acting confused
Difficulty breathing or wheezing
Very weak (can't stand)
Swollen tongue with rapid onset
Hoarseness or cough with rapid onset
Severe allergic reaction in the past to similar substance and hives present less than 2 hours

Call Your Doctor Now (night or day) If

You feel weak or very sick
Hives began after a bee sting, unusual food or medicine and no previous reactions

Call Your Doctor Within 24 Hours (between 9 am and 4 pm) If

You think you need to be seen
Hives interfere with school or normal activities after taking antihistamine (e.g., Claritin, Benadryl) every 6 hours for more than 24 hours
Fever, abdominal pain or joint swelling is present

Call Your Doctor During Weekday Office Hours If

You have other questions or concerns
Hives persist longer than 1 week
Unexplained hives have occurred 3 or more times in past year

Self Care at Home If

Hives with no complications and you don't think you need to be seen

HOME CARE ADVICE FOR HIVES

Localized Hives: For localized hives, wash the allergic substance off the skin with soap and water. If itchy, massage the area with a cold washcloth or ice. Localized hives usually disappear in a few hours and no further treatment is needed.
Widespread Hives - Take Antihistamine Medication: Take an antihistamine like over-the-counter loratadine (e.g., Claritin, Alavert) for widespread hives that itch. The adult dosage of loratadine is 10 mg by mouth once each day. Continue the antihistamine until the hives have been gone for 24 hours. Any antihistamine will do - but some cause more drowsiness than others. Loratidine is a newer (second generation) antihistamine and it causes less sedation than diphenhydramine (Benadryl) or chlorpheniramine (Chlortrimeton).
- Do not take anthistamines if you have prostate problems.
- Antihistamines may cause sleepiness. Do not drink, drive or operate dangerous machinery while taking antihistamines.
- Read the package instructions thoroughly on all medications that you take.
Cool Bath: Take a cool bath for 10 minutes to relieve itching (Caution: avoid any chill). Rub very itchy areas with an ice cube for 10 minutes.
Remove Allergens: Take a bath or shower if triggered by pollens or animal contact. Change clothes.
Avoid Allergens: If you identify a substance that causes hives, try to avoid that substance in the future.
Contagiousness: Hives are not contagious. You can return to work or school if the hives do not interfere with normal activities.
Expected Course: Hives normally come and go for 3 or 4 days, then disappear.
Call Your Doctor If:
- Severe itching persists longer than 24 hours while taking an antihistamine
- Hives persist longer than 1 week
- You become worse

And remember, contact your doctor if you develop any of the "Call Your Doctor" symptoms.

Disclaimer: This information is not intended be a substitute for professional medical advice. It is provided for educational purposes only. You assume full responsibility for how you choose to use this information.

Author and Senior Reviewer: David A. Thompson, M.D.

Last Reviewed: 9/21/2007

Last Revised: 3/21/2007

Content Set: Adult HouseCalls Online