Hives can occur anywhere on the body. However, they are particularly common on the arms and legs because the limbs have more exposure to external factors than can trigger the rash.

Hives, or urticaria, are raised rashes that can develop as red or purplish spots or patches. The rashes are often itchy and uncomfortable.

Hives typically occur when mast cells, which are part of the immune system, trigger an allergic reaction by releasing histamine into the skin. Histamine is a chemical messenger that the immune system releases in response to an injury or allergic reaction.

Mast cells cause hives and control how long they remain.

A similar process known as angioedema occurs when mast cells deeper in the skin release histamine.

Hives can develop due to an allergic reaction to food, medication, or something in the environment, such as being licked by a dog or from non-allergic sources, such as infection or inflammation.

Individual hives typically go away within 24 hours. However, urticaria can persist for several weeks, even months. This can result in new hives appearing as the previous ones fade.

Hives can occur anywhere on the skin. They are particularly common in areas of the body that experience higher pressure, such as the waistline and the groin.

Read on to learn more about the causes, types, and treatments of hives.

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Hives can result from:

  • physical triggers, such as pressure
  • allergic reactions, such as food allergies
  • medical conditions, such as infection

Triggers cause the immune system to respond by sending histamines and similar chemicals into the skin, where they cause hives. Triggers can include:

In rare cases, urticaria can be a hereditary condition.

When hives have no known cause, they are called idiopathic urticaria.

If hives only appear on the arms or legs, they are likely the result of a physical trigger, such as extreme temperature, or a contact allergen, such as latex.

Learn about contact dermatitis here.

Urticaria can be acute or chronic.

With acute urticaria, symptoms go away within 6 weeks. However, when a person has chronic urticaria, the condition can persist for longer than this.

There are three types of chronic urticaria:

  • Chronic spontaneous urticaria is where the trigger is unclear, and symptoms occur at least twice each week.
  • Chronic inducible urticaria is where specific, physical triggers, such as pressure, cause hives.
  • Episodic chronic urticaria can overlap with chronic inducible urticaria, but typically, symptoms appear less than twice each week.

Learn about hives on black skin here.

Treatment options include over-the-counter (OTC) medication, prescription medication, and home remedies.

OTC options include antihistamines, which people can take in higher doses than doctors typically recommend.

If OTC medication does not work, a doctor may prescribe:

However, medication may not always be necessary, as hives can go away by themselves. Home remedies that can help to ease symptoms include:

  • soothing the area with a cool compress
  • taking a comfortably cool bath
  • avoiding tight or itchy clothing and wearing loose, cotton clothes
  • avoiding particularly hot or cold temperatures
  • avoiding activities that cause sweating

Learn about ways to treat hives here.

It is not always possible to prevent hives from developing on the arms and legs, as around 50% of people with chronic urticaria never find out what causes their hives to appear. However, if there is a clear trigger, the most effective preventive measure is to try to avoid it.

Learn more about hives that come and go daily here.

See a doctor if:

  • hives continue to flare up for more than 6 weeks
  • OTC treatment is not helping
  • individuals want to check for potential allergies

Taking a photograph of hives before an appointment can help a doctor make a diagnosis, as the skin may clear up before the appointment.

If swelling underneath the skin accompanies a rash, a person may have angioedema. This condition can cause similar symptoms but requires swift treatment, as it can cause life threatening swelling that affects the ability to breathe.

Anyone who suspects they have angioedema should see a doctor for a diagnosis as soon as possible.

Severe allergic reactions can cause anaphylaxis, an extreme response that can cause a person to go into anaphylactic shock. Seek immediate medical attention if extreme symptoms develop.

Learn about the differences between urticaria and angioedema here.

Hives, or wheals, occur when the immune system sends histamines and other chemicals into the skin in response to triggers.

Urticaria can be acute, where it goes away within 6 weeks. Chronic urticaria lasts longer than this. The hives themselves disappear within 24 hours, but flare-ups may persist as new hives develop.

Physical triggers, allergic reactions, or medical conditions can cause hives, and they can develop anywhere on the body. The arms and legs are more likely to react to contact triggers, such as allergens, because they have greater exposure.

Hives can be itchy and uncomfortable, but they will generally go away on their own. Home remedies such as a cool compress can help to ease symptoms.

If urticaria symptoms continue, a doctor can suggest a treatment plan to help.