Think of your immune system like an army of cells ready to fight a threat. A virus or allergen invades your body and the cells attack.
Unfortunately, sometimes it might feel like they’re attacking you, especially when you end up covered in hives.
“Hives are raised bumps on the skin, usually red, and they can get pretty itchy,” says UNC Health allergist and immunologist Sofija D. Volertas, MD. “But they’re not as scary as they may look. It’s a sign that the immune system has been activated, most commonly to fight an infection.”
Dr. Volertas explains why hives appear and how you can make them go away.
What Causes Hives?
Hives are caused by histamine, a chemical released by the immune system that we tend to associate with allergies. But not every case of hives is an allergic response.
“The most common cause of hives is actually a virus, like a cold or an upper respiratory infection,” which also trigger histamine release, Dr. Volertas says. “Allergies to a food or medication also cause hives but are a less common cause compared to viruses.”
How long your hives last can be a clue as to whether they’re caused by an allergen or an infection.
“With an allergic reaction, hives generally appear a few minutes to two hours after the exposure, and they last for about 12 hours,” Dr. Volertas says. “We don’t see allergic reactions lasting longer than a day. For a virus or other infection, hives can last a few days in a row.”
About 1 percent of the population is affected by chronic spontaneous urticaria, or hives that appear on the body most days for more than six weeks. In this condition, the histamine is released without a trigger like a virus or allergen.
People with chronic hives may find their hives flare up as the result of certain triggers, including stress, lack of sleep, heat, exercise, medications (particularly aspirin and NSAIDs) or pressure on the skin from tight clothing or bags worn on the shoulder.
Heat in particular can cause a certain kind of hive “that looks like a pinprick or a pimple,” Dr. Volertas says, noting that these hives are typically an immune system response.
Not every raised, red bump on your skin is a hive; you might have a rash because of exposure to a skin irritant. Rashes tend to bring other changes to the skin, such as scaliness, dryness or blistering. They last longer than individual hives, and they may be painful, as opposed to itchy.
How to Treat Hives
Most of the time, hives on their own are not an emergency. But when they appear with other symptoms of an allergic response, they could indicate a severe allergic reaction known as anaphylaxis.
“It’s an emergency when the response involves another system—hives plus vomiting or diarrhea, or hives plus trouble breathing or tightness in your chest, or hives plus swelling in the eyes or lips,” Dr. Volertas says.
If you have a known allergy and these symptoms, administer epinephrine (many people carry an EpiPen but a new needle-free treatment is available); if you don’t, visit an emergency department or urgent care or call 911 right away.
If you’re experiencing hives as part of a known infection, like a cold, or if it’s your only response to a known allergen, you can reduce the itch and make the welts go away by taking an oral antihistamine. Cold compresses can help with the itch while you wait for the antihistamine to take effect (typically 20 to 30 minutes).
“Use second-generation antihistamines, like cetirizine (Zyrtec) or fexofenadine (Allegra),” Dr. Volertas says. “We don’t recommend diphenhydramine (Benadryl), which is a first-generation antihistamine. Those are short-lived and can cause drowsiness, but second-generation antihistamines work equally quickly, last longer and don’t cause drowsiness.”
Dr. Volertas says that she doesn’t typically recommend over-the-counter creams, because the reaction that is causing the hives is inside the body.
If your hives go away on their own, there’s no need to see a doctor. But if you’re bothered by persistent hives, talk to your provider. They can determine if you need allergy testing, an increased dose of an antihistamine, or possibly injections to keep chronic hives controlled; a drug called omalizumab (Xolair) is one injectable option.
While antihistamines help hives go away more quickly, they will resolve on their own.
“Individual hives typically go away in 24 hours, but even chronic spontaneous urticaria tends to go away on its own in one to five years,” Dr. Volertas says. “Hives heal themselves in either scenario.”
That doesn’t mean you have to see hives as inevitable—you can work to control flares by avoiding known triggers. If you realize you’re getting overheated, find a cool space out of the sun. If you know that stress causes your hives, practice taking deep breaths when you feel anxious or overwhelmed.
“Hives aren’t dangerous, but they are very uncomfortable,” Dr. Volertas says. “Scratching is going to make it worse. Most of the time, an over-the-counter antihistamine will do the job, but if that’s not working, an allergist will have some more options for management. If you’re miserable, we can help.”
If you have questions about your skin, talk to your doctor. If you need a doctor, find one near you.