Hives are red and sometimes itchy bumps on your skin.
An allergic reaction to a drug or food usually causes them. Allergic reactions cause your body to release chemicals that can make your skin swell up in hives. People who have other allergies are more likely to get hives than other people. Other causes include infections and stress.
Hives are very common. They usually go away on their own, but if you have a serious case, you might need medicine or a shot. In rare cases, hives can cause a dangerous swelling in your airways, making it hard to breathe - which is a medical emergency.
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.
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:
- Emotional stress
- Extreme cold or sun exposure
- Excessive perspiration
- Illness, including lupus, other autoimmune diseases, and leukemia
- Infections such as mononucleosis
- Exposure to water
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.
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.