What are hives?
Hives are raised welts that can appear anywhere on your skin and are usually itchy. The medical term for hives is urticaria. Hives are usually red or skin-colored, and they vary in size from a pea to a dinner plate. Look for a reddish halo surrounding the border of these itchy skin plaques. Hives are most often triggered by the release of histamines in the skin, which causes localized swelling, burning and itching. Hives can result from allergic reactions or may be due to many other conditions.
Individual welts or spots usually will not last more than a day, though new hives may appear, and the general condition can last for weeks depending on the cause. Many hives may join together to form a very large welt. Scratching, compressing, heating or cooling hives excessively can worsen them.
Though itchy and uncomfortable, hives are usually self-limiting and disappear on their own. In rare circumstances, hives can be a sign of a more serious allergic reaction wherein similar changes occur within the mouth, the airways, and the digestive tracts. A visit to your health care professional may help to determine what triggered your hives, though the exact cause is usually difficult to determine.
Seek immediate medical care (call 911) for serious symptoms, such as difficulty breathing or swelling of the tongue. These symptoms can be a sign of a serious allergic reaction known as anaphylaxis, which can be life threatening if not treated immediately.
Seek prompt medical care if you are being treated for hives but mild symptoms recur or are persistent.
What are the symptoms of hives?
Symptoms of hives include itching and swelling of the skin, causing raised red or skin-colored welts. The welts may come and go quickly and may resolve within hours or remain in some form for weeks. They can change rapidly in both size and number. Hives may have any shape, though they usually have well-defined borders. If you press on a hive, it will turn white (blanch), and then regain its reddish color when released.
Hives are present only on the skin and are usually not associated with diseases in other organs. On rare occasions, hives can be a sign of a serious allergic reaction resulting in similar changes that occur within the mouth, the airways, and the digestive tracts. Difficulty breathing, fainting, or swelling of the face or tongue may indicated a serious and potentially life-threatening allergic reaction and require immediate emergency care.
Common symptoms of hives
Hive symptoms may come and go within minutes, or they may persist for hours or even days. You may experience the symptoms often or just occasionally. Common symptoms of hives include:
Swelling in other parts of your body, including your hands, feet, or around your eyes
Welts that are raised and red or skin-colored
Serious symptoms that might indicate a life-threatening condition
In some cases, hives may be a symptom of anaphylaxis, which is a life-threatening condition. Seek immediate medical care (call 911) if you, or someone you are with, have any of these life-threatening symptoms including:
Sudden swelling of the face, lips or tongue
Tightness in your chest or throat
Wheezing (whistling sound made with breathing)
What causes hives?
Hives are often triggered by an allergy. An allergy causes the release of histamines, which dilate the blood vessels in your skin, thus increasing blood flow to the area. The increased blood flow causes the redness and swelling that appear as a hive on your skin. Additionally, histamines cause the itching that is often associated with hives.
The exact trigger that causes the skin reaction in any given person can be difficult to determine. Common allergens, such as pet dander, pollen, or shellfish and other foods, can cause hives, as can medications or bug bites. Your physician may be able to determine what triggers your hives in certain situations using blood tests or allergy testing.
What are the risk factors for hives?
Hives are extremely common, and anyone can get them. A number of factors increase the risk of developing hives. Not all people with risk factors will get hives. Risk factors and common triggers for hives include:
Adverse reaction to medication (ACE inhibitors, antibiotics, aspirin, NSAIDs, opioids)
Adverse reaction to radiocontrast dyes
Exposure to extreme cold
Reducing your risk of hives
Eliminating your exposure to known allergens may help reduce your risk of getting hives. A physician or health care professional may be able to determine what allergens you are sensitive to or what triggers your outbreaks so that you can avoid them.
You may be able to lower your risk of hives by:
- Avoiding common allergens
- Avoiding known triggers
- Reducing excessive sun exposure
How are hives treated?
Although hives can be very uncomfortable, they generally respond to treatment. Antihistamines can block the action of the chemical mediators that are responsible for hives. Certain steroids may also be effective in reducing hives. Additionally, you can reduce the discomfort associated with hives by avoiding hot or cold water or tight-fitting clothing.
Short-term control of hives and hive symptoms
Short-term treatment for hives includes antihistamines, which block the substances that cause the swelling and itching and can be very effective in reducing the discomfort of hives. Corticosteroids may also be used to reduce inflammation and discomfort. Short-term treatments include:
Antihistamines, such as diphenhydramine (Benadryl), which block the histamines that cause swelling and itching. Certain antihistamines may cause drowsiness, and it is best to select a nondrowsy medication for infrequent hives.
Topical steroids, such as cortisone creams, which reduce inflammation and may be effective in reducing the discomfort associated with hives
Long-term control of hives and hive symptoms
Rarely, a person may have prolonged or frequent hives. In these cases, more powerful antihistamines are frequently prescribed. Certain antihistamines may cause drowsiness, and it is best to select a non-drowsy medication for infrequent hives.
If you have frequent or persistent hives, your health care professional may perform diagnostic tests for infections or autoimmune diseases that may be contributing to the formation of hives. Long-term control of hives may include:
Antihistamines, such as diphenhydramine (Benadryl), which block the histamines that cause swelling and itching
Diagnosis and appropriate treatment of any underlying conditions that contribute to the formation of hives
Emergency treatment for severe hives
In rare cases, hives may be associated with difficulty breathing or swelling of the tongue. These are serious symptoms that could indicate a systemic allergic reaction known as anaphylaxis. Emergency treatment of these dangerous symptoms may include:
What you can do to improve your hives
In addition to reducing your exposure to situations or substances that trigger your hives, you can reduce symptoms of hives by:
- Avoiding extreme cold
- Avoiding extreme sun
- Wearing loose-fitting clothing
What are the potential complications of hives?
Hives may appear as a symptom of anaphylaxis, which is a life-threatening, body-wide allergic reaction. Anaphylaxis may be associated with swelling of the face, tongue or airway, which may make breathing difficult or impossible.
If you have a history of allergies, you should avoid common allergens, such as pollen or pet dander. You should also avoid any allergens to which you are sensitive, even if they have not caused severe symptoms in the past. You can help minimize your risk of serious complications by following the treatment plan you and your health care professional design specifically for you. Complications of anaphylaxis include:
- Respiratory failure and respiratory arrest
- Unconsciousness and coma