However, chronic hives often have different outcomes, and unfortunately, while about 50% of hives resolve within a year of entering the chronic phase, some people will have hives for life. “With chronic hives, we can rarely identify why they’re happening, and the longer someone has hives, the less likely they are to go away,” Friedman says, adding that 20% can last more than 10 years.

The causes of hives are numerous and can be separated into allergic and non-allergic reactions. Allergens that cause hives include food, medications, insect bites and stings, pollen, animals, contact with something you are allergic to (think latex, for example), and even allergy shots, according to the American Academy of Dermatology. (3) People who suffer from hives are advised not to take certain medications, such as aspirin or NSAIDs, as these medications can make hives worse. (4)

Nonallergic causes include bacterial and viral infections; exercise; stress; pressure on the skin or scratching; chemical contact; exposure to sun, heat, or cold; and autoimmune diseases such as thyroid disease and lupus, particularly in the case of chronic hives.

Among this list, however, three are perhaps the most common, and Friedman sums it up in a simple phrase: “Food, medicine and insects,” he says.

Stress can also contribute to hives.

Stress may be a factor in hives, but it is usually not an independent risk factor.

“Stress is usually not the direct cause and primarily affects people who are susceptible to hives,” says Friedman. Both chronic and acute hives can be made worse by stress, especially in people who are more likely to get hives, such as women and people with autoimmune disorders. (5)

On the other hand, however, hives can be so difficult to deal with physically, emotionally, and mentally that it can easily make you more stressed, even cause you to sleep less, and affect your mood as a result. This can lead to problems getting along with family, coworkers, and friends. That’s why stress management can be key in helping to alleviate some of these issues – and can often help control hives.

The majority of cases of hives will go away on their own. (6) Individual hives usually go away within about 24 hours, and cases of hives should stop going away and coming back within a few weeks.

If hives persist for more than six weeks, they could be chronic or a sign that something else is going on. It’s a good idea to see a doctor if hives last that long. (1)

Also see your doctor if a single hive lasts more than 24 hours and is painful, or if the welts cause discomfort. (6)

When you see a doctor about hives, expect a physical exam. The doctor may recommend additional blood and skin tests to determine if there is an underlying problem or cause for the hives. Some cases of long-term hives may benefit from a skin biopsy to help determine the cause. If the cause of the hives is known (such as an allergen trigger), you may not need additional testing. (7)

Duration of hives

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

Hives also move around, and they don’t necessarily care what part of the body they inhabit. Even your scalp, the soles of your feet, and the palms of your hands can get hives. “If you see one moving around a lot, that’s a sign of a hive,” Friedman says.

Acute hives last less than six weeks, while chronic hives last more than six weeks. This doesn’t mean you’re covered in hives every day during these periods, but it does mean that during these times, the hives come and go erratically or sometimes more constantly, says Anthony M. Rossi, MD, an attending dermatologist at Memorial Sloan Kettering Cancer Center in New York City.

Fortunately, although they can be very itchy, hives do not leave any marks on the skin once they have gone away, whether you have treated them or not.

Hives are neither contagious nor, in most cases, dangerous. There are, however, some exceptions that should prompt emergency care.

The first is a condition called angioedema, which involves swelling of the tissues under the skin. This can cause swelling of the tongue, lips, throat, hands, feet, and even the inside of the abdomen. As a result, people may experience stomach cramps or, worse, difficulty breathing. People with hives can have angioedema, but note that “just because you have hives doesn’t mean you’ll have angioedema,” says Dr. Rossi.

If hives are accompanied by swelling and breathing becomes difficult, seek emergency care immediately.

Hives can also be the result of a severe allergic reaction called anaphylaxis, Rossi says. If you experience difficulty breathing; swelling of the lips, tongue, or eyelids; dizziness; abdominal pain; or nausea or vomiting in conjunction with hives, seek help immediately.