Hives are raised, often itchy, red bumps (welts) on the surface of the skin. They are usually an allergic reaction to food or medicine. They can also appear without cause.
Urticaria; Wheals; Nettle rash; Angioedema; Quincke edema
When you have an allergic reaction to a substance, your body releases histamine and other chemicals into the blood. This causes itching, swelling, and other symptoms. Hives are a common reaction. Persons with other allergies, such as hay fever, often get hives.
When swelling or welts occur around the face, especially the lips and eyes, it is called angioedema. Swelling can also occur around your hands, feet, and throat.
Many substances can trigger hives, including:
- Animal dander (especially cats)
- Insect bites
- Shellfish, fish, nuts, eggs, milk, and other foods
Hives may also develop as a result of:
Often, the cause of hives is not known.
Symptoms of hives may include any of the following:
- Swelling of the surface of the skin into red- or skin-colored welts (called wheals) with clearly defined edges.
- Wheals may get bigger, spread, and join together to form larger areas of flat, raised skin.
- Wheals can also change shape, disappear, and reappear within minutes or hours.You know you have hives when you press the center of a wheal, it turns white. This is called blanching.
Dermatographism is a type of hives. It is caused by pressure on the skin and results in immediate hives.
Exams and Tests
Your health care provider can tell if you have hives by looking at your skin.
If you have a history of an allergy, the diagnosis is even clearer.
Sometimes, a skin biopsy or blood tests are done to confirm that you had an allergic reaction, and to test for the substance that caused the allergic response.
Treatment may not be needed if the hives are mild. They may disappear on their own. To reduce itching and swelling:
- Do not take hot baths or showers.
- Do not wear tight-fitting clothing, which can irritate the area.
- Your provider may suggest that you take an antihistamine such as diphenhydramine (Benadryl). Follow your provider's instructions or the package instructions about how to take the medicine.
If your reaction is severe, especially if the swelling involves your throat, you may need an emergency shot of epinephrine (adrenaline) or steroids. Hives in the throat can block your airway, making it difficult to breathe.
Hives may be uncomfortable, but they are usually harmless and disappear on their own. In most cases, the exact cause of hives cannot be identified.
When the condition lasts longer than 6 weeks, it is called chronic hives. Often, no cause can be found.
- Anaphylaxis (a life-threatening, whole-body allergic reaction that causes breathing difficulty)
- Swelling in the throat can lead to life-threatening airway blockage
When to Contact a Medical Professional
Call 911 or your local emergency number if you have:
- Shortness of breath
- Tightness in your throat
- Tongue or face swelling
Call your health care provider if the hives are severe, uncomfortable, and do not respond to self-care measures.
To help prevent hives:
- Avoid exposure to substances that give you allergic reactions.
- Do not wear tight-fitting clothing and do not take hot baths or showers just after having hives. These can cause hives to return.
Grattan CEH. Urticaria and angioedema. In: Bolognia JL, Jorizzo JL, Schaffer JV, eds. Dermatology. 3rd ed. Philadelphia, PA: Elsevier Saunders; 2012:chap 18.
Saini SS. Urticaria and angioedema. In: Adkinson NF Jr., Bochner BS, Burks AW, et al, eds. In: Middleton's Allergy Principles and Practice. 8th ed. Philadelphia, PA: Elsevier Mosby; 2014:chap 36.
Reviewed By:Kevin Berman, MD, PhD, Atlanta Center for Dermatologic Disease, Atlanta, GA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
The information provided herein should not be used during any medical emergency
or for the diagnosis or treatment of any medical condition. A licensed medical professional
should be consulted for diagnosis and treatment of any and all medical conditions. Call 911
for all medical emergencies. Links to other sites are provided for information only -- they
do not constitute endorsements of those other sites. © 1997-A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
The Agency for Health Care Administration (Agency) and this website do not claim the information on, or referred to by, this site is error free. This site may include links to websites of other government agencies or private groups. Our Agency and this website do not control such sites and are not responsible for their content. Reference to or links to any other group, product, service, or information does not mean our Agency or this website approves of that group, product, service, or information.
Additionally, while health information provided through this website may be a valuable resource for the public, it is not designed to offer medical advice. Talk with your doctor about medical care questions you may have.