What Are Hives? Symptoms, Causes, Diagnosis, Treatment, and Prevention

• Acute hives last anywhere from under one day to less than six weeks.

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• Chronic hives occur two or more times a week for longer than six weeks.

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   Most people with chronic hives never know what's causing them, a form known as chronic spontaneous hives. “With chronic hives, we can rarely identify why they're happening, and the longer somebody has hives, the less likely it is that they'll go away,” says Adam Friedman, MD, a professor of dermatology at the George Washington University School of Medicine and Health Sciences in Washington, DC, adding that 20 percent of people with chronic hives have them for longer than 10 years.
• Physical, or inducible, hives can be triggered by extreme cold, heat, or sun exposure, as well as intense exercise, sweating, vibrations, or pressure. They often appear within an hour of exposure. Inducible hives might also be chronic.

• Red or skin-colored bumps or welts that typically clear up within 24 hours but may reappear in another spot
• Raised patches or spots that can be the size of a pinhead or as wide as a dinner plate
• Bumps or welts that show up either alone or in clusters, covering a larger area
• Intense itchiness around the bumps or welts that can severely affect quality of life, sleep, and mental health

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• Swelling around the bumps or welts
• Burning pain or stinging at the site of the bumps or welts

Hives share symptoms with other conditions, but a few characteristics are specific to hives, including how long they last and their tendency to disappear from one area and pop up in another. “Although many conditions can look like hives, they often don't behave like hives,” says Dr. Friedman.

Hives start when the immune cells in your body called mast cells activate. In many cases, those mast cells release a chemical called histamine that can cause swelling, itching, and redness. Hives show up to help control the body's allergic response to specific triggers.

Although not all hives result from histamine release, most do, says Sarina B. Elmariah, MD, PhD, a board-certified dermatologist, associate professor of dermatology at the University of California in San Francisco, and research affiliate at Massachusetts General Hospital in Boston. “Hives can be a response to allergic triggers but can also be a reaction to internal changes without an identifiable allergic trigger. Not every individual who gets hives needs to have food allergy testing, which is a common misunderstanding in patients and even some doctors,” says Dr. Elmariah.

Friedman sums up the three most common causes of acute hives in one simple phrase: “Food, drugs, and bugs,” he says.

• Food
• Medication
• Insect bites and stings
• Pollen
• Animal fur or dander
• Touching something you're allergic to such as latex
• Allergy shots

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Nonallergic causes include the following:

• Bacterial and viral infections
• Sweat
• Stress
• Pressure on or scratching the skin
• Chemical contact
• Exposure to the sun
• Heat
• Cold
• Autoimmune disorders like thyroid diseases and lupus, which are especially likely to play a role in chronic hives

For longer-lasting or severe hives, a dermatologist or allergist will likely follow these steps:

• Perform a physical exam, as they can often identify hives at a glance
• Ask questions regarding possible exposures to allergens
• Recommend blood and skin tests to rule out allergies, illness, or infections.

Some people with a single longer-lasting lesion may benefit from a skin biopsy to help determine the cause, as individual hives very rarely last longer than 24 hours, according to Friedman.

How you treat hives depends on how many you've had and how long they've been active.

Medication

Medications for hives include antihistamines, steroids, epinephrine, and monoclonal antibodies.

Over-the-Counter Antihistamines

• diphenhydramine (Benadryl)
• loratadine (Claritin)
• fexofenadine (Allegra)
• cetirizine (Zyrtec)
• levocetirizine (Xyzal)

If you have one patch of hives that goes away within 24 hours and no associated breathing issues, you probably don't need medical attention. Instead, you might take an OTC nonsedating antihistamine to ward off a second hive outbreak, Friedman says. “It's more about prevention or active treatment,” he says.

Epinephrine

If you notice hives and breathing difficulties, head to the emergency room or seek other urgent care. Medical professionals will most likely inject you with epinephrine. This drug opens the airways in your lungs.

Corticosteroids

Monoclonal Antibodies

These injectable prescription medications can help reduce the immune overactivity that causes allergy symptoms and soothe itching over time when other medications have not been effective.

• dupilumab (Dupixent)
• omalizumab (Xolair)

Researchers are studying other monoclonal antibody drugs for treating hives.

Off-Label and Emerging Medications

Off-label drugs are those that the U.S. Food and Drug Administration (FDA) has approved for treating conditions other than hives. However, doctors may prescribe them if chronic hives don't respond to approved treatments.

• cyclosporine (Neoral, Sandimmune)
• methotrexate (Rheumatrex, Trexall)
• azathioprine (Imuran)
• mycophenolate mofetil (CellCept)
• dapsone
• hydroxychloroquine (Plaquenil)
• TNFα inhibitors (Enbrel, Humira)

Elmariah is enthusiastic about progress toward new treatments that reduce the sensitivity of mast cells to various triggers,  preventing the release of histamine in the first place. “Other medications, including a pill option known as remibrutinib, are far along in development, have demonstrated tremendous benefit for patients with hives, and may get FDA approval soon,” she says.

Phototherapy

Phototherapy, or light therapy, involves exposing the skin to a controlled dose of ultraviolet light. A doctor may recommend it for treating hives that don't respond to antihistamines.

Managing Hives in Children

• cetirizine, either in liquid or tablet form
• diphenhydramine liquid, capsules, or tablets, although these can cause drowsiness
• fexofenadine tablets
• loratadine tablets

No matter the treatment course, avoid the urge to scratch the hives. “You risk breaking the skin and getting an infection,” Friedman says.

• Ice packs
• A cool cloth
• A cool shower
• A moisturizer that's spent time in the fridge to cool it down

You can prevent acute hives if you know what's triggering them. “If you can identify your trigger, the best prevention strategy is to avoid triggers,” Friedman says.

“A hive lesion doesn't usually last much longer than 24 hours, whereas things like bug bites, which are easily confused with hives, can last several days,” Friedman says. That means you might wake up with a hive one morning, and that one specific hive may be completely gone by the next morning, Friedman says, adding that they often appear without any warning.

Although they might itch a lot, hives don't leave any marks on the skin once they resolve, regardless of whether you received treatment for them or not.

Hives are neither contagious nor, in most cases, dangerous. However, a few complications of hives can develop in some people and should prompt emergency care.

Angioedema

Anaphylaxis

• Difficulty breathing or swallowing
• Swelling of your lips, tongue, or throat
• Dizziness
• Abdominal pain
• Nausea or vomiting in conjunction with hives
• A tight chest
• Cramps
• Diarrhea
• A sense of impending doom
• Wheezing
• Unconsciousness
• Cardiac arrest
• Lightheadedness and confusion
• Sudden-onset weakness

Certain conditions and other things can trigger hives or occur alongside hives:

• Allergies Acute hives often occur as part of an allergic reaction. The trigger could be certain foods, medicines, fabrics, pollen, animals, or insect bites.

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• Stress This can increase your body's histamine response, which can make hives worse in people who already have a risk of them. Relaxation techniques may help reduce the risk.

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• Chronic Infections Long-term, underlying infections, such as Helicobacter pylori, may have links to chronic spontaneous hives.

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   Viral infections may cause hives along with fever, cough, or diarrhea, and bacterial infections like urinary tract infections (UTIs) and strep can also lead to hives.

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• Celiac disease
• Dermatomyositis
• Diabetes
• Lupus
• Polymyositis
• Rheumatoid arthritis
• Thyroid disease
• Vitiligo

• Hives are an extremely common immune response that can affect anyone.
• Hives are red or skin-colored welts that feel itchy and are occasionally painful.
• Keep track of and avoid potential triggers, including stress and certain foods, animals, or medications, to help prevent hives.
• Hives often last 24 hours, so an OTC antihistamine or cold therapy can help.
• See a doctor about long-lasting or multiple hives along with breathing problems, as they may need to prescribe medication.