Urticaria, also known as hives, is an outbreak of pale red bumps or welts on the skin that appear suddenly. The swelling that often comes with hives is called angioedema.
If you’ve had red or skin-colored bumps that appeared and disappeared quickly, then it’s unlikely to be simple bug bites. The skin rash could be hives, and the itching from hives may range from mild to severe. Hives, also known as urticaria, affects about 20 percent of people at some time during their lives. Scratching, alcoholic beverages, exercise and emotional stress may worsen the itching. If you think you might have hives, then it’s best to speak with an allergist.
You likely know hives for the way they appear on your skin: They’re red, swollen welts that can sometimes be accompanied by itchiness or pain. There are a variety of possible causes for hives (or reasons that histamine and other chemicals get released by the body in the first place). They could be the result of allergies in response to foods, medication, or an infection, or they could be from another trigger, like exercise, heat, stress, or alcohol.
When an allergic reaction occurs, the body releases a protein called histamine. When histamine is released, the tiny blood vessels known as capillaries leak fluid. The fluid accumulates in the skin and causes a rash.
Hives often appear suddenly on any part of the body. They may appear in one place, go away in a few hours and then come back in another place. In severe cases, hives may come and go for several weeks. For most people, they are not serious.
Physicians arbitrarily divide hives into acute (new or periodic episodes lasting fewer than 6 weeks) and chronic (periodic episodes lasting more than 6 weeks). Though many people have a single episode of acute hives that goes away within a few days to weeks, some individuals may have chronic hives that persist intermittently for years. More often than not, the offending agent is never identified in those who suffer from chronic hives.
The condition is considered chronic hives if the welts appear for more than six weeks and recur frequently over months or years. Often, the cause of chronic hives is not clear.
Chronic hives can be very uncomfortable and interfere with sleep and daily activities. For many people, antihistamines and anti-itch medications provide relief.
Allergic reactions, chemicals in certain foods, insect stings, sunlight, and medications can cause hives. It’s often impossible to find out exactly why hives have formed.
What Are Hives?
Hives (medically known as urticaria) appear on the skin as wheals that are red, very itchy, smoothly elevated areas of skin often with a blanched center. They appear in varying shapes and sizes, from a few millimeters to several centimeters in diameter anywhere on the body.
It is estimated that 20% of all people will develop urticaria at some point in their lives. Hives are more common in women than in men. One hallmark of hives is their tendency to change size rapidly and to move around, disappearing in one place and reappearing in other places, often in a matter of hours. An individual hive usually lasts no longer than 24 hours. An outbreak that looks impressive, even alarming, first thing in the morning can be completely gone by noon, only to be back in full force later in the day.
Very few skin diseases occur and then resolve so rapidly. Therefore, even if you have no evidence of hives to show the doctor when you get to the office for an examination, the diagnosis can be established based upon the accurate recounting of your symptoms and signs. Because hives fluctuate so much and so fast, it is helpful to bring along a photograph of what the outbreak looked like at its most severe point.
Swelling deeper in the skin that may accompany hives is called angioedema. This swelling of the hands and feet, as well as the face (lips or eyelids), can be as dramatic as it is brief.
What Are the Symptoms of Hives?
“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.”
Usually the welts will be surrounded by clear edges. They may look similar to bug bites, but hives generally will appear and disappear more quickly. They may itch, sometimes severely, and they’re 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 grouped together and take over a large area of the skin, or 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 over and over again (usually as a result of a specific trigger).
Generally, you’ll know you have hives simply by seeing the hives themselves. If you experience other symptoms, such as swelling in 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, a dermatologist at Spring Street Dermatology in New York City. These symptoms indicate you may be experiencing a serious allergic reaction called anaphylaxis.
What Causes Hives?
Hives are the body’s response to an irritation. The cause (trigger) may be non-allergic or allergic.
Non-allergic hives are the most common type. Usually, their exact cause is unknown. Some causes of non-allergic hives are:
- Viruses and infections
- Temperature extremes – hot and cold
- Sunlight – sunlamps or direct sunlight
- Pressure – skin that is rubbed very hard or scratched or clothes are too tight-fitting
- Emotional stress
Allergic hives have a known cause, but are less common. Some causes of allergic hives are:
- Foods – especially peanuts, eggs, tree nuts, milk or shellfish
- Medicines – antibiotics and pain medicines
- Plants – grass and weeds
- Insect stings or bites
- Animal dander
- Chemicals – soaps, detergents and lotions
Allergy-induced urticaria occurs when the immune system responds abnormally to an otherwise harmless substance and releases a chemical known as histamine into the bloodstream.5 Histamine is an inflammatory substance that causes the symptoms of allergy, affecting the respiratory system, gastrointestinal tract, and skin.
Common triggers of allergy-induced urticaria include food (including shellfish, eggs, and nuts), drugs (including aspirin and antibiotics), and insect bites (especially bees and fire ants).
Chronic Idiopathic Urticaria
Chronic urticaria is often idiopathic and may be worsened in times of stress.6 The exact pathway of the condition is unknown. In some patients, autoantibodies (immune proteins that target the body’s own cells) are found in blood, but these autoantibodies are not necessarily disease-causing. Testing for these autoantibodies is generally discouraged because positive results do not diagnose chronic urticaria or help in routine treatment decisions.
While the instigating cause of chronic urticaria may be different from allergy-induced urticaria, the outcome will be the same (albeit longer-lasting). Women tend to be affected more than men.
In some cases, the trigger is obvious – a person eats peanuts or shrimp, and then breaks out within a short time. Other cases require detective work by both the patient and the physician because there are many possible causes. If the hives have gone on for a long time, the cause is not usually identified.
A single episode of hives does not usually call for extensive testing. If a food allergy is suspected, consider keeping track of what you eat. This will help you discover whether there is a link between what you’re eating and when you break out with hives.
Chronic hives should be evaluated by an allergist, who will ask about your and your family’s medical history, substances to which you are exposed at home and at work, exposure to pets or other animals and any medications you’ve taken recently. If you have been keeping a food diary, show it to your allergist.
Your allergist may want to conduct skin tests, blood tests and urine tests to identify the cause of your hives. If a specific food is the suspected trigger, your allergist may do a skin-prick test or a blood test to confirm the diagnosis; once the trigger is identified, you’ll likely be advised to avoid that food and products made from it. In rare instances, the allergist may recommend an oral food challenge – a carefully monitored test in which you’ll eat a measured amount of the suspected trigger to see if hives develop.
If a medication is suspected as the trigger, your allergist can conduct similar tests, and a cautious drug challenge – similar to an oral food challenge, but with medications – may also be needed to confirm the diagnosis. Because of the possibility of anaphylaxis, a life-threatening allergic reaction, these challenge tests should be done only under strict medical supervision, with emergency medication and equipment at hand.
In cases where vasculitis (inflammation of the blood cells) may be the cause, your allergist may conduct a skin biopsy and send it to a specialist to examine under a microscope.
The cause of chronic hives is often difficult to identify.
How Are Hives (Urticaria) Treated?
Most of the time, hives and swelling go away without treatment. Your healthcare provider might recommend medications and at-home care to help you feel better and lower your chances of having hives again. Treatments include:
- Allergy medications: Medicines called antihistamines block histamine’s effects on your body. Antihistamines relieve itching from hives and prevent allergic reactions. Some antihistamines react fast, like diphenhydramine (Benadryl®). Depending how severe the hives are, your healthcare provider may recommend daily over-the-counter (OTC) or prescription allergy medications, like loratadine (Claritin®). fexofenadine (Allegra®), cetirizine (Zyrtec®) or levocetirizine (Xyzal®).
- Allergy shots: For hard-to-treat chronic hives, your healthcare provider may recommend a monthly injection of a drug called omalizumab (Xolair®). This medication blocks the body’s allergy antibody, immunoglobin E (IgE), from causing allergy reactions. People with severe allergies can make too much IgE, leading to problems like hives and asthma.
- At-home treatments: To relieve hives, you can take a cool bath or shower, wear loose-fitting clothing and apply cold compresses. An OTC hydrocortisone cream, such as Cortizone®, can relieve itching and swelling.
- Epinephrine: Severe allergic reactions and swelling can lead to a life-threatening condition called anaphylaxis. Symptoms include hives, swelling, shortness of breath, wheezing, vomiting and low blood pressure. People experiencing anaphylaxis need an immediate epinephrine injection (EpiPen®) to open a swollen airway.
- Oral steroids: Corticosteroids, such as prednisone, can relieve hive symptoms that don’t respond to antihistamines.
Researchers have identified many – but not all – of the factors that can cause hives. These include food and other substances you take, such as medications. Some people develop hives just by touching certain items. Some illnesses also cause hives. Here are a few of the most common causes:
- Some food (especially peanuts, eggs, nuts and shellfish)
- Medications, such as antibiotics (especially penicillin and sulfa), aspirin and ibuprofen
- Insect stings or bites
- Physical stimuli such as pressure, cold, heat, exercise or sun exposure
- Blood transfusions
- Bacterial infections, including urinary tract infections and strep throat
- Viral infections, including the common cold, infectious mononucleosis and hepatitis
- Pet dander
- Some plants
Antihistamines – available either over the counter or by prescription – are a frequently recommended treatment for hives. They work by blocking the effect of histamine, a chemical in the skin that can cause allergy symptoms, including welts. Antihistamines that don’t make you drowsy are preferred. They are effective and long-lasting (may be taken once a day) and have few side effects. Your allergist may recommend a combination of two or three antihistamines to treat your hives, along with cold compresses or anti-itch balms to ease the symptoms.
Severe episodes of urticaria may require temporary treatment with prednisone, a similar corticosteroid medication or an immune modulator, which can reduce the severity of the symptoms.
If your reaction involves swelling of your tongue or lips, or you have trouble breathing, your allergist may prescribe an epinephrine (adrenaline) auto-injector for you to keep on hand at all times. These can be early symptoms of anaphylaxis, a potentially fatal allergic reaction that impairs breathing and can send the body into shock.
The only treatment for anaphylaxis is epinephrine. If you develop hives and your injector is not nearby – or if using the auto-injector doesn’t cause the symptoms to immediately improve – call 911 or go to an emergency room immediately. Emergency medical services carry epinephrine and can provide prompt treatment. You should also go to the emergency room after using an auto-injector.
If the cause of hives can be identified, the best treatment is to avoid the trigger or eliminate it:
- Foods: Don’t eat foods that have been identified to cause your symptoms.
- Rubbing or scratching: Avoid harsh soaps. Frequent baths may reduce itching and scratching – beneficial because itching and scratching can make the hives feel worse.
- Constant pressure: Avoid tight clothing. Pressure hives can be relieved by wearing loose-fitting clothes.
- Temperature: If you develop hives when exposed to cold, do not swim alone in cold water and always carry an epinephrine auto-injector. Avoid exposure to cold air and use a scarf around your nose and mouth in cold weather. If you must be out in the cold, wear warm clothing.
- Sun exposure: Wear protective clothing; apply sunblock.
- Medications: Notify your physician or pharmacist immediately if you suspect that a specific medication is causing your hives.
Simple changes to your lifestyle may be able to help you prevent hives from reoccurring in the future. If you have allergies and you know which substances are likely to cause an allergic reaction, your doctor will suggest that you avoid any possible exposure to these factors. Allergy shots are another option that may help you reduce the risk of experiencing hives again.
Avoid being in high-humidity areas or wearing tight clothing if you have recently had a hives outbreak.