Hives (medically known as urticaria) appear on the skin as wheals which 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 inches 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.
Individual hives usually last 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, if any other 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 examination, he or she can often establish the diagnosis based upon the history of your symptoms. Because hives fluctuate so much and so fast, it is helpful to bring along a photograph of what the outbreak looked like at its worst.
Swelling deeper in the skin that may accompany hives is calledangioedema. This swelling may be seen on the hands and feet, as well as the lips or eyes, that can be as dramatic as it is brief.
As is true with any skin allergy, the mast cells of the skin begin to produce chemical called “histamine” which gives the appearance of hives on the skin. When the body has an allergic reaction of hives then there is a sudden onset of skin welts and raised red colored or pale colored bumps. These bumps mostly resemble mosquito bites and are itchy too. In fact, most of the people first mistake skin hives as normal mosquito bites.
But the glaring difference between skin hives and mosquito bites is that the sizes of the welts keep changing. It is also seen that the location of the hives shift from legs to arms or vice-versa. These welts last for a day or so and keep changing their locations. Sometimes, severe forms of hives result in swelling in lips, moth area, face and the tongue. This is called as angioedema.
Swelling of the face is the most common symptom in hives where the patient gets swollen cheeks and the glands too get irritated.
As noted above, many cases of ordinary hives are "idiopathic", meaning no cause is known. Others may be triggered by viral infections. A few may be caused by medications, usually when they have been taken for the first time a few weeks before. It is uncommon for drugs taken continuously for long periods to cause hives or other reactions.
When a medication is implicated as a cause of hives, the drug must be stopped, since no skin or blood test will prove the connection. In most cases, drug-induced hives will go away in a few days. If a drug is stopped and the hives do not go away, this is a strong indication that the medication was not in fact the cause of the hives.
Some medications, like morphine, codeine, aspirin, and other nonsteroidal anti-inflammatory drugs (NSAIDs, such as ibuprofen [Advil]), cause the body to release histamine and produce urticaria through nonallergic mechanisms.
Despite the reputation hives have for being "allergic", when there is no obvious connection between something new that a person has been exposed to and the onset of hives, allergy testing is not usually helpful.
Chronic hives (defined as lasting six weeks or more) can last from months to years. The evaluation of this condition is difficult and allergy testing and other laboratory tests are rarely useful in such cases. The accurate evaluation of this condition requires the patient to give his or her physician precise information regarding their complete medical history, personal habits, and oral intake. Occasionally it may be necessary to limit specific foods or drugs for a time to observe any affect upon the skin condition.
Certain systemic disease and infections may occasionally present in the skin as hives. If there is an inciting cause that can be determined, then specific treatments for that condition ought to be effective, or in the case of food or drug allergy, strict avoidance would be necessary. There are additionally rare forms of chronic urticaria that are produced when the patient makes antibodies against molecules on the surface of their own mast cells. There are tests available to identify this type of hives.
Physical urticaria is a type of chronic urticaria produced by physical stimuli. By far the most common form is dermographism, which literally means "skin writing". This is an exaggerated form of what happens to anyone when their skin is scratched or rubbed: a red welt appears at the line of the scratch.
In dermographism, raised, itchy red welts with adjacent flares appear wherever the skin is scratched or where belts and other articles of clothing rub against the skin, causing mast cells to leak histamine.
Another common form of physically induced hives is called cholinergic urticaria. This produces hundreds of small, itchy bumps. These occur within 15 minutes of exercise or physical exertion and are usually gone before a doctor can examine them. This form of hives happens more often in young people.
Other forms of physical hives are much less common. Triggers for these include cold, water, and sunlight.
Hives are produced when histamine and other compounds are released from cells called mast cells, which are normally found in the skin. Histamine causes fluid to leak from the local blood vessels, leading to swelling in the skin.
Hives are very common. Although they can be annoying, they usually resolve on their own over a period of weeks and are rarely medically serious. Some hives are caused by allergies to such things as foods, medications, and insect stings, but in the majority of cases, no specific cause for them is ever found. Although patients may find it frustrating not to know what has caused their hives, maneuvers like changing diet, soap, detergent, and makeup are hardly ever helpful in preventing hives and are not necessary for the most part.
Having hives may cause stress, but stress by itself does not cause hives.
In rare cases (some hereditary, others caused by bee stings or drugallergy), urticaria and angioedema are accompanied by a striking decrease in blood pressure (shock) and difficulty breathing. This is called anaphylaxis. Ordinary hives may be widespread and disturbing to look at, but the vast majority of cases of hives do not lead to life-threatening complications.
The goal of treating most cases of ordinary urticaria is to relieve symptoms while the condition goes away by itself. The most commonly used oral treatments areantihistamines, which help oppose the effects of the histamine leaked by mast cells. The main side effect of antihistamines is drowsiness.
Many antihistamines are available without prescription, such asdiphenhydramine (Benadryl), taken in doses of 25 milligrams and chlorpheniramine (Chlor-Trimeton), taken in a dose of 4 milligrams.
These can be taken up to three times a day, but because these medications can cause drowsiness, they are often taken at bedtime. Those who take them should be especially careful and be sure they are fully alert before driving or participating in other activities requiring mental concentration.
Loratadine (Claritin, 10 milligrams) is an antihistamine available over the counter that is less likely to cause drowsiness. Also approved for over-the-counter use is hydroxyzine (Atarax, Vistaril), which causes drowsiness, and its breakdown product, cetirizine (Zyrtec, 10 milligrams), which is mildly sedating.
Antihistamines that require a prescription include cyproheptadine (Periactin), which tends to cause drowsiness. Prescription antihistamines that cause little sedation are fexofenadine (Allegra) and levocetirizine (Xyzal).
Sometimes physicians combine these with other types of antihistamines called H2 blockers, such as ranitidine (Zantac) and cimetidine (Tagamet). This antihistamine list is not exhaustive. Physicians individualize treatment plans to suit specific patients and modify them depending on the clinical response.
Oral steroids (prednisone, [Medrol]) can help severe cases of hives in the short term, but their usefulness is limited by the fact that many cases of hives last too long for steroid use to be continued safely.
Other treatments have been used for urticaria as well, including montelukast (Singulair), ultraviolet radiation, antifungal antibiotics, agents that suppress the immune system, and tricyclic antidepressants (amitriptyline [Elavil, Endep], nortriptyline [Pamelor, Aventyl], doxepin [Sinequan, Adapin]). Evidence to support the benefit of such treatments is sparse. In ordinary cases, they are rarely needed.
Topical therapies for hives are available but are generally ineffective. They include creams and lotions which help numb nerve endings and reduceitching. Some ingredients which can accomplish this are camphor, menthol,diphenhydramine, and pramoxine.
Many of these topical preparations require no prescription. Cortisone-containing creams (steroids), even strong ones requiring a prescription, are not very helpful in controlling the itch of hives.