By: Christine Haran
Last Reviewed on: April 26, 2005
Some people break out in hives whenever they share a room with a cat. Others find themselves covered in these itchy red bumps when they?re feeling stressed. While stress-induced hives usually resolve on their own, other types of hives require treatment that can range from antihistamines to oral steroids. Most of the time hives are short-term, but some people suffer from chronic hives that can last for years, leading to problems such as sleep loss and depression.
Hives are usually part of an allergic reaction that occurs when a chemical called histamine is released by cells in the body called mast cells. The release of histamine can be triggered in response to a variety of stimuli, including certain foods, medication, or even temperature.
Below, Dr. Barbara Muller, professor of allergy-immunology at the University of Iowa Hospitals in Iowa City, discusses common causes of hives and treatment approaches for short-term and chronic hives.
What are hives?
Hives are raised, itchy wheal-and-flare reactions on the skin medically referred to as "urticaria." The lesions look and itch similar to mosquito bites. They can be very small, a few millimeters in size, or become quite large, several centimeters in size, especially with scratching. Separate lesions often merge to involve an entire portion of an extremity, such as a foot or hand, or extend to the abdomen or trunk. The itching associated with hives is bothersome and can be intense. If severe, an outbreak can include symptoms such as fatigue, chills or joint aches.
Individuals who develop hives may also suffer from a condition called "angioedema." where swelling occurs in the deeper layers of the skin. Swelling can be severe and lead to deformity of a portion of the face, lips, eye area, or genitalia. If swelling occurs in the throat, breathing may be affected and medical attention must be sought immediately.
How long do hives last?
An individual hive should not last longer than 24 hours. Yet a hive outbreak can develop suddenly and last a few hours or days, or continue for weeks or months at a time. Hives lasting less than six weeks are referred to as acute. Outbreaks can also be long-term, or chronic, lasting longer than six weeks. If you have chronic hives it may a sign of an underlying non-allergic condition. Hives can reoccur often over years.
What causes hives?
Acute cases of hives that come on suddenly and are short-term are generally caused by an allergic reaction to food or medication, or by contact with or exposure to an allergen in your environment.
Basic food allergy is a common trigger of hives. Tree nuts, including brazil nuts, walnuts, cashews, and almonds, or legumes such as peanuts are common causes of allergic reactions. Allergies to seafood, particularly shrimp, lobster, crawfish, and mollusks, are also commonly reported. Eggs, milk, soy, cheese, wheat, strawberries, and tomatoes are all known to cause hives in susceptible individuals.
Rarely, preservatives or additives in foods cause hives. People can be sensitive, for example, to tartrazine, yellow dye #5, or other coloring additives found in many processed foods such as candies and puddings. Keeping track of what you eat each day with a food diary can help an allergist pinpoint the foods that trigger hives outbreaks.
Allergic reactions to medications are a commonly reported cause of hives. Penicillin, cephalosporins (semi-synthetic penicillins), aspirin, non-steroidal anti-inflammatory drugs such as ibuprofen, opiates and muscle relaxants may produce acute reactions in susceptible individuals. If you begin a new medication and develop hives or red blotches on the skin, report the reaction to your prescribing physician immediately, before taking another dose.
Other triggers include various ingredients used in the manufacturing of cosmetics and fragrances, as well as bee or wasp venom. People with an insect allergy may develop a serious reactions if stung. It is important to seek medical attention promptly if you suspect you are having an allergic reaction.
What role can the environment have on the development of hives?
Environmental triggers, such as animal dander, dust mites, pollen, mold spores, and reactions to chemical irritants or odors, can also cause hives in sensitive individuals.
Some individuals who have "physical urticarias" develop hives in response to various physical stimuli in the environment. This type of hives is usually long-lasting and likely to recur. Pressure, vibration, cold, heat, water, exercise, sunlight, temperature changes, and other physical stimuli can provoke hives.
Does stress/anxiety cause hives?
Stress, anxiety, excitement, and emotional situations can all cause changes in the body?s nervous system, making them capable of producing hives in certain individuals. These outbreaks are generally short-term and resolve on their own.
When can hives be a sign of underlying disease?
Patients with chronic hives may have an underlying disease that has gone undiagnosed. Certain health conditions such as a thyroid disorder, hepatitis, viral infection, or even cancer can produce hives. Children with viral infections are especially susceptible to hive outbreaks. Hives have also been associated with parasitic, fungal, and bacterial infections. Interestingly enough, there?s evidence that women are more likely to suffer hives in the premenstrual period, or around the time that they?re going through menopause.
If no allergies or obvious physical triggers are uncovered in the initial clinical exam, your doctor can perform a basic laboratory evaluation to see whether there is an underlying disease.
What are treatment steps for acute hives?
Treatment will depend on the cause and severity of symptoms. Of course, you should avoid contact with the particular substance associated with the development of the hives. Generally speaking, a mild case of a few hives can be controlled rather quickly by taking antihistamines. It would be helpful to use a hypoallergenic skin moisturizer and avoid scratching, which can make the hives worse.
On the other hand, people can have a full-blown acute reaction where they are very sick with a massive breakout of hives on the skin, intense itching, and progressing symptoms including headache, dizziness, vomiting, and flu-like symptoms. In some cases, an allergic reaction can develop almost within minutes, and that can cause life-threatening symptoms such as breathing difficulties and swelling in the throat. In these cases, go to the nearest hospital emergency room immediately or call 911. Patients with a history of recurrent serious reactions are usually prescribed an EpiPen, an adrenaline syringe that temporarily alleviates symptoms until the patient can get professional medical care. Patients should have the device with them at all times for immediate use when symptoms begin.