What Are Hives?
Hives are red raised bumps or welts on the skin. Hives (or urticaria ) is a common skin reaction to something like an allergen (a substance that causes allergies).
The spots can appear anywhere on the body and can look like tiny little spots, blotches, or large connected bumps.
Individual hives can last anywhere from a few hours to a week (sometimes longer), and new ones might replace those that fade. Hives that stay for 6 weeks or less are called acute hives; those that go on longer than 6 weeks are chronic hives.
What Causes Hives?
An allergic reaction can cause hives, as can:
- temperature extremes
- some illnesses
In some cases, a person has hives and angioedema, a condition that causes swelling around the eyes, lips, hands, feet, or throat. Very rarely, hives and angioedema are associated with an allergic reaction that involves the whole body or anaphylactic shock.
The red welts of hives happen when mast cells in the bloodstream release the chemical histamine, which makes tiny blood vessels under the skin leak. The fluid pools within the skin to form spots and large welts. This can happen for a number of reasons. But in many cases the cause is never found.
Most often, hives are associated with an allergic reaction, which can make the skin break out within minutes. Common allergies include:
- foods, especially shellfish, peanuts and tree nuts, milk, and fruit
- medicines (antibiotics) and allergy shots
- pets and other animals
- insect bites and stings
Sometimes a breakout of hives has nothing to do with allergies. Other causes include:
- infections, including viruses
- anxiety or stress
- sun exposure
- exposure to cold, such as cold water or snow
- contact with chemicals
- scratching (dermatographia)
- putting pressure on the skin, such as from sitting too long or carrying a heavy backpack over a shoulder
Hives due to physical causes (such as pressure, cold, or sun exposure) are called physical hives.
It can be hard to figure out what causes chronic urticaria, though it's 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.
What Are the Signs & Symptoms of Hives?
The hallmark red raised welts are the main sign of hives. The welts can:
- have a pale center
- appear in clusters
- change shape and location in a matter of hours
- be tiny or as big as a dinner plate
- itch, sting, or cause a burning sensation
Someone who also has angioedema might have puffiness, blotchy redness, swelling, or large bumps around the eyes, lips, hands, feet, genitals, or throat. Other symptoms can include nausea, vomiting, or belly pain.
Rarely, a person with hives and angioedema can also get anaphylactic shock. Signs of anaphylactic shock include breathing trouble, a drop in blood pressure, dizziness, or a loss of consciousness (passing out).
How Are Hives Diagnosed?
Most of the time, a doctor can diagnose hives just by looking at the skin. To find the cause, you may be asked questions about your child's medical history , recent illnesses, medicines, exposure to allergens, and daily stressors.
If your child has chronic hives, the doctor may ask you to keep a daily record of activities, such as what your child eats and drinks, and where the hives tend to show up on the body. Diagnostic tests — such as blood tests, allergy tests, and tests to rule out conditions that can cause hives, such as thyroid disease or hepatitis — might be done to find the exact cause of the hives.
To check for physical hives, a doctor may put ice on your child's skin to see how it reacts to cold or place a sandbag or other heavy object on the thighs to see if the pressure will cause hives.
How Are Hives Treated?
In many cases, mild hives won't need treatment and will go away on their own. If a definite trigger is found, avoiding it is part of the treatment. If the hives feel itchy, the doctor may recommend an antihistamine medicine to block the release of histamine in the bloodstream and prevent breakouts.
For chronic hives, the doctor may suggest a non-sedating (non-drowsy) prescription or over-the-counter antihistamine to be taken every day. Not everyone responds to the same medicines, though, so it's important to work with the doctor to find the right one for your child.
If a non-drowsy antihistamine doesn't work, the doctor may suggest a stronger antihistamine, another medicine, or a combination of medicines. In rare cases, a doctor may prescribe a steroid pill or liquid to treat chronic hives. Usually this is done for just a short period (5 days to 2 weeks) to prevent harmful steroid side effects.
In Case of Emergency
Anaphylactic shock and bad attacks of hives or angioedema are rare. But when they happen, they need immediate medical care.
Kids with bad allergies should carry an injectable shot of epinephrine . The doctor will teach you and your child how to safely give an injection if your child is at risk for a severe allergic reaction.Back to Articles
Learning About Allergies
During an allergic reaction, your body's immune system goes into overdrive. Find out more in this article for kids.Read More
Shellfish allergies can be serious - and shellfish can appear in some surprising foods and products. Read about shellfish allergy and what to do when a reaction is severe.Read More
Your eyes itch, your nose is running, you're sneezing, and you're covered in hives. The enemy known as allergies has struck again.Read More
Help With Hives
Hives are red, itchy blotches that can appear because of an allergic reaction. Find out more in this article for kids.Read More
Learn about rashes in a flash. Check out our article just for kids!Read More
First Aid: Allergic Reactions
Although most allergic reactions aren't serious, severe reactions can be life-threatening and can require immediate medical attention.Read More
Hives cause raised red bumps or welts on the skin. They're pretty common and usually not serious. Find out what to do about hives in this article for teens.Read More
Blood Test: Immunoglobulin E (IgE)
The immunoglobulin E (IgE) blood test is often done as part of an initial screen for allergies. High IgE levels also may indicate a parasitic infection.Read More
What Is Skin Testing for Allergies?
A scratch or skin prick test is a common way doctors find out more about a person's allergies.Read More
Serious Allergic Reactions (Anaphylaxis)
A person with severe allergies can be at risk for a sudden, serious allergic reaction called anaphylaxis. This reaction can seem scary, but the good news is it can be treated.Read More
Doctors are diagnosing more and more people with food allergies. Knowing what to expect and how to deal with food allergies can make a big difference in preventing serious illness.Read More
Struggling with strawberries? Petrified of peanuts? Sorry you ate shellfish? Maybe you have a food allergy. Find out more in this article for kids.Read More
Going to School With Food Allergies
With preparation and education, a child with a food allergy can stay safe at school.Read More
Food allergies can cause serious and even deadly reactions in kids, so it's important to know how to feed a child with food allergies and to prevent reactions.Read More
Helping your child manage an egg allergy means reading food labels carefully, being aware of what he or she eats, and carrying the right medicines in case of an allergic reaction.Read More