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Diseases & Conditions

Hives (Urticaria)

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When Eddie woke up with itchy red bumps on his arm and back, his mom told him it was just a case of hives and it would be gone in a few days. After a couple of weeks, though, the hives weren’t any better. Eddie’s mom thought he should see a doctor.

The doctor looked at Eddie’s skin and asked him some questions about his recent activities and his diet. He told Eddie that he had chronic urticaria — the medical name for long-lasting hives — and prescribed an antihistamine to treat it.

What Is Urticaria?

The medical name for hives is urticaria. It’s a common condition that causes raised red bumps or welts to appear on the skin (some hives have a pale center as well).

Top Things to Know About Hives

Hives can be itchy; sometimes they also burn or sting. Usually, they’re harmless and last anywhere from half an hour to a couple of days. New hives can show up to replace the old ones as they fade, though. So the condition can go on for a while.

Doctors put hives into two categories:

  1. Acute hives: when the condition lasts for less than 6 weeks (also called “acute urticaria”).
  2. Chronic hives: when the condition lasts for longer than 6 weeks (“chronic urticaria”).

How Do You Know It’s Hives?

The raised red bumps that we call hives can appear anywhere on the body. Here are some signs to watch for:

  • Hives often itch or sting.
  • Hives can range in size from as small as a few millimeters across to as big as a dinner plate.
  • Individual hives may change shape or appear in clusters. Sometimes hives join together to form larger patches.
  • Hives can spread or show up on a different part of the body.

In a few rare cases, hives are part of a serious allergic reaction called anaphylaxis.

What Causes Hives?

Most often, people get hives as part of an allergic reaction. Hives also can be the body’s way of reacting to temperature extremes, stress, infections, or illnesses.

The red blotches happen when cells in the bloodstream (called mast cells) release the chemical histamine. This causes tiny blood vessels under the skin to leak. The fluid pools within the skin to form spots and larger blotches.

Acute Hives

When an allergic reaction causes hives, they usually show up within minutes. Things (called triggers) that can cause someone to have hives include:

Sometimes hives have nothing to do with allergies. Other causes include:

  • infections, including colds
  • anxiety or stress
  • exposure to the sun
  • exposure to cold, such as from diving into a cold pool
  • exercise
  • contact with chemicals
  • scratching
  • putting pressure on the skin, such as from sitting too long or carrying a heavy bag over a shoulder

It’s not always obvious why someone has hives. If hives come and go quickly, most people don’t give them much thought. But chronic hives (those that last for more than a few weeks) can be more worrying.

Chronic Hives

Chronic urticaria is sometimes linked to an immune system illness, like lupus. Other times, medicines, food, insects, or an infection can trigger an outbreak. Often, though, doctors don’t know what causes chronic hives. The good news is, hives can be treated.

How Do Doctors Diagnose Hives?

Usually a doctor will look at a person’s skin and be able to say it’s hives without doing anything else. With chronic hives, the doctor will ask more questions to find out why they’ve been going on for so long. He or she also may do some tests, like blood tests or allergy tests, to rule out other conditions.

A doctor may put ice on a person’s skin to see how it reacts to cold or place a sandbag or other heavy object on the thighs to see if pressure causes hives to appear.

If you have chronic hives, the doctor may ask you to keep a diary that includes:

  • your daily activities
  • everything you eat and drink
  • where hives appear on your body

How Are Hives Treated?

Some cases of hives go away on their own without treatment. If something is definitely causing a person to get hives, the doctor will recommend avoiding that trigger.

If hives are very itchy, the doctor may recommend taking an antihistamine medicine to block the release of histamine in the bloodstream. For chronic hives, doctors may prescribe a non-sedating (non-drowsy) or over-the-counter antihistamine to take every day.

The same medications don’t work for everyone, though. If you have chronic hives, it can take time and patience for you and your doctor to figure out the right treatment. If a non-sedating antihistamine doesn’t work, your doc might suggest a stronger antihistamine or another medication or a combination of medicines.

In rare cases, a doctor may prescribe a steroid pill or liquid to treat chronic hives. Usually, this will only be done for short periods (5 days to 2 weeks).

When It’s an Emergency

Anaphylaxis and severe attacks of hives require immediate medical care. People who know they have serious allergies may need to carry an injectable shot of epinephrine for use in emergencies.

Fortunately, serious attacks of hives are extremely rare. Most of the time, hives are completely harmless and go away on their own. Even chronic hives can sometimes clear up on their own within a few months to a year.

Reviewed by: Rupal Christine Gupta, MD
Date reviewed: August 2014