What are hives?
Hives (referred to by physicians as urticaria) are red, very itchy swellings that occur in groups on any part of the skin. A simple uncomplicated hive lasts up to a few hours before fading away without leaving a trace. New hives may continue to develop as the old areas fade. Hives can vary in size from as small as a pencil eraser to as large as a dinner plate and may join together to form larger swellings. There is always some discomfort accompanying each hive described typically as itching, but may also be burning or stinging.
A hive is caused by fluid leaking through tiny gaps in the blood vessels of the skin. The blood vessels dilate because of inflammation. The source of the inflammation can be allergic or non-allergic. If the leakage is very deep in the skin, there is mostly swelling, indicating angioedema. If the leakage is more superficial, a typical hive develops. Both types of reactions can occur simultaneously. Swelling is more common in the lip and around the eyes, especially in the morning, whereas hives can be found on any part of the body. Angioedema can be particularly threatening if it occurs in the throat or lung where breathing may become impaired.
Inflammation causes a variety of natural chemicals to be produced, particularly histamine. This is why physicians commonly prescribe antihistamines to control hives. However, histamine is not the only naturally occurring chemical capable of causing hives. It is for this reason that antihistamines do not always work for hives and more potent broad spectrum anti-inflammatory medications such as steroids must be used occasionally.
Hives are a very common medical condition affecting one out of every five Americans at some time in their lives. The difficulty lies in understanding the cause of the hives in each individual case. Virtually every disease or allergy known to man is capable of causing a hive reaction in some people because the human body naturally triggers inflammation to fight problems. This is why it is extremely important for your physician to know your medical history. Without accurate information, trying to diagnose the cause of hives can be like looking for a needle in a haystack.
How are hives diagnosed?
Hives are diagnosed by their appearance and classified according to how long the attacks last and how frequently they occur. The term “acute urticaria” refers to a bout of hives lasting less than six weeks. Frequently, an underlying cause can be identified by history and eliminated in acute urticaria. To find the cause, both you and your physician must become detectives. This is particularly difficult if your hives are chronic (more than six weeks in duration). The most common identified causes of hives are foods, drugs, infections and physical urticaria (described below). Rarely, chronic hives or angioedema may be part of a more serious illness or an inherited problem. Many types of hives are actually a change in the immune system in which a person develops a self-antibody triggered by a drug or a virus that attacks cells in the skin like an allergy and cause the hive reaction. This type usually slowly resolves over months to years. The following are some types or causes of hives that have been described by doctors.
- Food & Food Additives: The most common foods that cause hives are nuts, fish, shellfish, eggs, peanuts, milk, chocolate, citrus, and fresh berries. The association of food additives and hives is unclear because of a lack of reliable scientific confirmation. Additives suggested as possible causes of hives are tartrazine (yellow dye #5), monosodium glutamate (MSG), nitrates, nitrites, BHT and sulfites. The diagnosis usually is obvious with the help of a food diary taken each time hives occur.
- Drugs: Virtually any medication (prescription or over-the-counter) can cause hives. The drugs most commonly associated with hives are aspirin and all aspirin-like drugs (ibuprofen, naproxen, etc., but not acetaminophen), antibiotics, sedatives, tranquilizers, and anti-hypertensive medications. It is important to realize that antacids, vitamins, eye drops, laxatives, vaginal douches, and all of the remedies found in a health food store should be considered medications capable of causing hives. Again, history is the most important method of diagnosing a drug-induced hive problem. It is always important to review all your medication and consider any new medications from a physician or even the health food store that was used just prior to the hives beginning. Even a recent blood transfusion or immunization can cause hives.
- Infections: Many infections cause hives. Viral respiratory infections are particularly common causes of hives in children. Other infections such as hepatitis, syphilis, along with a wide number of other infections have been incriminated as well. Recent vaccinations for infectious diseases can also cause a hive reaction.
- Physical Urticaria: Certain people can develop hives from sunlight, cold, pressure, vibration, water, or exercise. The physical urticaria can last from several months to a lifetime in people who are otherwise healthy.
Hives due to sunlight, referred to as solar urticaria, is an uncommon disorder in which hives develop within minutes of sun exposure and fade again within one or two hours. Sometimes a medication is being taken simultaneously which acts as the triggering event with sunlight.
Cold urticaria is more common. Hives appear when the skin is warmed after cold exposure or generalized chilling. If the exposure to cold is over large areas of the body, as in swimming, large amounts of histamine can be released with life-threatening potential.
Cholinergic urticaria is the term applied to tiny, about 1/8th inch, bumps surrounded by a large red or white area (halo) which comes on with exercise, heat or emotion. These bumps itch intensely. Anything that raises the skin temperature can cause these tiny hives: sweating, sunlight, hot baths, blushing, or anger, for example. Hives can also be caused by pressure, vibration, and even water contact. Again, a carefully obtained history usually describes this relationship.
The most common form of physical urticaria is dermographism. It affects about five percent of people. In dermographism, swelling develops from firm stroking or scratching of the skin. These swellings may be very itchy. Dermographism can also be seen along with other forms of urticaria. If dermographism is present with urticaria, finding and eliminating the cause of the hives will usually clear the dermographism. Otherwise dermographism, like the other forms of physical urticaria, may persist for months or even years.
How are hives treated?
The best treatment of hives is to find the cause and eliminate it. Unfortunately, this is not always possible. Usually, the longer the hives have been present, the harder it is to find the cause. Your physician will need to ask numerous questions in an attempt to identify a possible cause. You will also be asked to participate in detective work. If your hives are chronic or an acute cause can be tested for, your physician may ask you to have various laboratory tests in addition to taking your history and performing a physical examination. If a cause cannot be found or eliminated, antihistamines and sometime other types of medications will be prescribed. There are many antihistamines available. They will vary in price, how often they are taken, and their potential to cause drowsiness. It is important to take your antihistamines regularly unless told to do otherwise by your physician. For acute relief, an injection of epinephrine (Adrenalin) may be given. An oral steroid may also bring dramatic relief from hives in severe cases. However, the administration must be limited to short periods of time and a rebound of your hives may occur when this drug is stopped. Ultimately, most hives are simply controlled with medications and eventually, most hives go away by themselves. It is very uncommon for a hive problem to last a lifetime even when the cause cannot be found.
How are hives avoided?
Unless a hive problem is caused by a food, chemical or medication that is identified and eliminated, there is no way of preventing hives. That is because the vast majority of chronic hives are due to your body’s own immune system making an allergy antibody to some unknown event such as a viral infection. The good news is that the body usually forgets about making this antibody eventually, causing the hive problem to subside. However, this can take from days to years to occur.