Hives

911 warning

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Does this describe your symptoms?

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Itchy swollen patches or bumps that appear suddenly.
Patches change shape and location frequently; any one patch generally only lasts for a few hours then fades away.
Size of patches varies from a 1/2 inch to several inches across.
In Caucasians and individuals with lighter skin tones, hives appear pink or red in color, with a central area of paleness (welts).

General

The medical term for hives is "urticaria".
Hives are often an allergic skin reaction to something that the patient has eaten, touched, or in some other manner been exposed to. Hives are not contagious.
Hives usually come and go for several days to a week. Sometimes they can reappear weeks or months later. Some individuals have "chronic urticaria", and symptoms can be intermittently present for months.

Causes of Hives

Localized: Localized hives are usually due to skin contact with plants, pollen, food, a chemical or pet saliva. Dermographism is the term used to describe patients who have localized hives in response to firm stroking of the skin. Localized hives are not caused by drugs, infection or swallowed foods. Localized hives usually resolve in less than 4 hours.
Widespread: Widespread hives can be an allergic reaction to a food, cosmetic product, drug, insect bite, or other substance. Sometimes widespread hives shows up after a viral infection. Stress may bring on or aggravate hives. Often the cause is not found (idiopathic).

Definitions

Anaphylactic Reaction: Anaphylaxis is a serious allergic reaction that is rapid in onset and may cause death.
Severe Allergic Reaction: Any associated symptoms besides skin findings: swollen tongue, shortness of breath, syncope, abdominal pain.
Localized Hives: Hives on one area of the body only.
Widespread Hives: Hives on multiple (2 or more) areas of the body.

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	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 Life-threatening reaction (anaphylaxis) in the past to similar substance (e.g., food, insect bite/sting, chemical, etc.) and less than 2 hours since exposure
	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 Hives have become worse and taking oral steroids (e.g., prednisone from doctor) for 24 hours
	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

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Food Related Hives:
- Foods can cause transient hives, especially around the mouth.
- Some are mild food allergies; others can occur in anyone (e.g., with strawberries).
- Hives from foods usually disappear within 6 hours.
Antihistamine (e.g., Benadryl) for Hives from Food:
- One or two dosages of an antihistamine will accelerate the clearing of this type of hives.
- Benadryl (diphenhydramine) is an antihistamine. The adult dose is 25-50 mg. If the hives are still present after 6 hours, repeat the Benadryl.
- If Benadryl is not available, use any hay fever or cold medicine that contains an antihistamine. Examples of other antihistamines are chlorpheniramine (Chlortrimeton, Chlor-tripolon) and loratadine (Claritin, Alavert). Loratadine is a newer (second generation) antihistamine and it causes less sedation than diphenhydramine.
- CAUTION: This type of medication may cause sleepiness. Do not drink alcohol, drive or operate dangerous machinery while taking antihistamines. Do not take these medications if you have prostate enlargement.
- Read the package instructions thoroughly on all medications that you take.
Prevention: In the future, avoid any food you think caused the hives.
Call Your Doctor If:
- Severe hives or severe itching persist more than 24 hours despite taking an antihistamine (e.g., Benadryl).
- You become worse.

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 don't need treatment with an oral antihistamine (e.g., Benadryl).
Hydrocortisone Cream:
- For very itchy spots, apply hydrocortisone cream 4 times a day as needed.
- It is available over-the-counter in U.S. as 0.5% and 1% cream.
- Available over-the-counter in Canada as 0.5% cream.
Prevention: Try to avoid any substance that you think caused the hives.
Call Your Doctor If:
- Severe hives or severe itching persist more than 24 hours despite taking an antihistamine (e.g., Benadryl).
- Hives last more than 1 week.
- You become worse.

Widespread Hives:
- Remove allergens. For widespread hives be certain to take a bath or shower, if triggered by pollens or animal contact. Change clothes.
- Take a cool bath for 10 minutes to relieve itching. Rub very itchy areas with an ice cube for 10 minutes.
- Hives normally come and go for 3 or 4 days, then disappear.
Antihistamine (e.g., Claritin) for Widespread Hives:
- Take an antihistamine like loratadine (e.g., OTC 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.
- Loratidine is a newer (second generation) antihistamine and it causes less sedation than diphenhydramine (Benadryl) or Chlorpheniramine (Chlortrimeton).
- CAUTION: This type of medication may cause sleepiness. Do not drink alcohol, drive or operate dangerous machinery while taking antihistamines. Do not take these medications if you have prostate enlargement.
- Read the package instructions thoroughly on all medications that you take.
Contagiousness: Hives are not contagious. You can return to work or school if the hives do not interfere with normal activities.
Prevention: If you identify a substance that causes hives, try to avoid that substance in the future.
Call Your Doctor If:
- Severe itching persists more than 24 hours while taking an antihistamine
- Hives persist more than 1 week
- You become worse.

Updated:

March 22, 2017