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Doctors call it "urticaria," but everyone else calls it "hives." We're talking about the incredibly itchy, swollen rash that can suddenly show up on skin, without warning, only to disappear and show up hours later in the same place or another area of skin entirely.

Often, hives start out as small raised bumps about the size of your fingertip. These can quickly multiply and merge into large welts or "wheals" that can be found on the upper arms and legs, the stomach and chest, and on the back and buttocks.

If you have a light or medium skin tone, hives may look reddish or pink. If your skin has brown or black tones, hives may be the same color, or slightly lighter or darker.

Bottom line? Hives are common, and it is estimated that 1 in 5 men, women, and children worldwide will get hives at some point in their lives.

Are Hives Dangerous?

Hives are not contagious, and the vast majority of cases resolve completely in about a week, often without treatment. However, about 40% of people who develop hives also develop swelling of tissues at deeper levels, including the soft, moist "mucous membrane" tissues that line the eyelids, mouth, and throat.

This condition, called angioedema, can cause lips and eyes to become noticeably swollen, creating a burning, stinging sensation rather than an itch. This also tends to resolve within a few days, but in some cases can lead to a life-threatening allergic reaction known as anaphylaxis. Symptoms of dizziness, trouble breathing, and swelling of the tongue, lips, mouth, or throat signal the need for immediate medical care. Head to the nearest emergency department.

What Causes Hives?

Hives are often caused by an allergic reaction to food, medication, or common allergens such as pet dander, pollen, or even a bug bite. For this reason, people who have hay fever, asthma, or food allergies are thought to be at increased risk of hives.

Having an infection such as a head cold, strep throat, a urinary tract infection, or even COVID-19 can also lead to hives, as can medical conditions such as thyroid disease and lupus. Other "triggers" for hives include exposure to cold, heat, perspiration, or pressure on the skin from tight clothing.

Any of these factors can signal the immune system to activate mast cells in the skin, causing the release of histamine and other chemicals that lead to the development of hives. In spite of all that we know about the cause of hives, however, what causes 50% of acute hives and 80-90% of chronic hives remains a mystery.

How Long Do Hives Last?

Usually, hives disappear completely within 24 hours, but sometimes they come and go on an almost daily basis for up to 6 weeks. This is known as "acute" hives, and represents about 80% of all hives cases. Anyone can develop hives at any age, but acute hives are most common in children up to 5 years old.

When hives last longer than 6 weeks, they are classified as "chronic." These are most often seen in adults ages 20-40, with women affected twice as much as men. Again, symptoms tend to come and go on a daily or almost daily basis, but chronic hives can last for years, and can have a significant impact on quality of life and productivity at work and school.

What About Treatment?

Non-sedating antihistamines are a standard therapy for all types of urticaria, with omalizumab (Xolair), a monthly injectable, recommended in patients who don't respond to antihistamines. In 50% of patients with chronic hives, symptoms can be resolved or improved within a year.

For More Resources on Hives:

"Medical Journeys" is a set of clinical resources reviewed by physicians, meant for the medical team as well as the patients they serve. Each episode of this journey through a disease state contains both a physician guide and a downloadable/printable patient resource. "Medical Journeys" chart a path each step of the way for physicians and patients and provide continual resources and support, as the caregiver team navigates the course of a disease.