Hives, known in the medical world as urticaria, are your skin’s reaction to histamine (a chemical released by the body’s immune system in response to an allergen) and other inflammatory signals being released into your bloodstream. You likely know hives for the way they appear on the skin: They’re red, swollen welts that can sometimes be accompanied by itchiness or pain.
There are a variety of possible causes of hives (or reasons that histamine and other chemicals get released by the body in the first place). They could be a result of allergies in response to foods or medications, an infection, or another trigger, such as exercise, heat, stress, or alcohol.
Red bumps on the skin are a somewhat generic description. Couldn’t that indicate several possible skin issues? How do you know if you’re experiencing hives and not something else? Here’s what to know about hives and their unique symptoms.
“Hives are characterized by red or pale-colored welts on the skin, which typically come and go throughout the day,” says Sourab Choudhury, DO, a dermatologist and the chief medical officer at The Dermatology Specialists, a private dermatology practice in New York City. “Sometimes they itch, burn, or sting.” On Black or brown skin, hives may appear purplish in color, may match your skin tone, or may appear slightly lighter or darker than your skin tone.
Usually, the welts will be surrounded by precise edges. They may look similar to bug bites, but hives will generally appear and disappear more quickly. They may itch, sometimes severely, and they are not always the same size or shape. They may be as small as the tip of a pen or as large as a dinner plate. When you press the center of a hive bump on the skin, it likely will turn from red to white, which is known as blanching.
Hives may appear on the body in groups and take over a large area of skin, or they may occur as a couple of individual welts that show up here and there. They can appear anywhere on the body, though some people get them in the same spot repeatedly, usually due to a specific trigger.
You may be able to tell if you have hives simply by seeing the hives themselves. If you experience other symptoms, such as swelling of the eyes, lips, or inside of the throat, or if you have trouble breathing, you should call 911 or see a doctor immediately, says Sapna Palep, MD, founder and medical director at Spring Street Dermatology in New York City. These symptoms indicate that you may be experiencing a severe allergic reaction called anaphylaxis.
How Long Do the Symptoms Last?
Acute (short-term) hives will usually disappear within 24 hours. It might seem longer, though, because new hives may appear as old ones disappear. In total, hives can last anywhere from a few days to a few weeks.
If you have chronic hives, however, they will last for longer than six weeks. They may be recurring and come up seemingly at random over many months or years.
“To the untrained eye, hives can have a similar appearance to other common skin conditions,” Dr. Choudhury says. He says one way to tell the difference is by how quickly the welts clear up.
“Hives will usually have an area of skin that welts up, goes away in a few hours, and then reappears somewhere else,” he says. He explains that other skin issues that are often mistaken for hives tend to last for more than one day — and remain in the same location.
Also, check out the welts up close. “If the welts are filled with clear fluid, pus, or are brownish in color, it is likely not hives,” says Dr. Palep.
Hives are often mistaken for the following skin issues:
Angioedema is swelling of tissue deep in the skin. An allergic reaction, certain medicines, or a genetic disposition usually cause it. Generally, angioedema is characterized by swollen lips, eyelids, hands, throat, or feet, and trouble breathing.
Eczema (atopic dermatitis) is common among children but can affect adults too. Severe itchiness (especially at night), fluid-filled bumps, and red to brownish-gray patches indicate eczema rather than hives.
Bug bites may resemble hives, but hives tend to behave differently. Hives may change shape and move around the body, whereas a bug bite stays in the same place.
Rosacea usually appears as redness on the face, where swollen blood vessels become visible. It’s most common among middle-aged women with fair skin. The bumps look like acne and may contain pus, which hives generally do not. There is another form of rosacea called Morbihan disease, characterized by a firm edema on the upper part of the face, which may also be mistaken for hives.
Heat rash (also known as prickly heat or miliaria), typically appears in hot and humid weather, as the name suggests. Like hives, heat rash will appear as red bumps on the skin, although heat rash among adults generally occurs in areas where sweat gets trapped, such as in the armpits, elbow creases, and groin. It can also happen when a person wears tight clothing or has their back up against a chair for an extended period.
Contact dermatitis is a skin reaction that results from direct contact with something you’re allergic to, such as soap, jewelry, or a plant. Blisters may accompany the rash, which typically lasts between two and four weeks, whereas hives will come and go within 24 hours.
Acute hives (the ones that clear up within six weeks or less) can be straightforward and may not require medical attention. But sometimes hives warrant a visit to the doctor — or even the emergency room, in severe cases. It’s a good idea to visit your primary care doctor if the hives continue appearing over several days or if you experience severe symptoms and discomfort.
If the rash tends to pop up on and off again over some time, you may want to visit an allergist or dermatologist. They will likely run special tests to identify possible triggers causing the breakout.
Be on the lookout for more threatening symptoms too. If you suspect angioedema (mentioned above), you should go to the emergency room immediately. You should also seek emergency care if the hives are associated with an allergic reaction and include other symptoms, such as dizziness; swollen lips, eyes, and tongue; or anything that makes it hard to breathe. A good rule of thumb is that if you’re having trouble breathing, you should go to the emergency room or call 911, Choudhury says.
Hives, also known as urticaria, are red, swollen, itchy bumps that may appear in groups on the skin. They are a reaction to inflammatory signals in the bloodstream.
Other skin conditions, such as eczema or rosacea, are often mistaken for hives but appear and behave differently.
See a healthcare provider if hives continue appearing over several days or if you experience more severe symptoms like angioedema.
