Hives are raised, often itchy, red welts on the surface of the skin. They are usually an allergic reaction to food or medicine. Substances that can trigger hives include medications, shellfish, eggs, nuts, fish, milk, pollen, animal dander, and insect bites. Symptoms include itching and swelling of the surface of the skin into the red- or skin-colored welts (called wheals) with clearly defined edges. The welts may enlarge, spread, and join together to form larger areas of flat, raised the skin. They can also change shape, disappear, and reappear within minutes or hours. The welts tend to start suddenly and resolve quickly. When you press the center of a red welt, it turns white.
Dr. Green Dermatology - Urticaria (Hives)Hives are very common with 10-20 percent of the population having at least one episode in their lifetime. Hives can sometimes occur in deeper tissues of the eyes, mouth, hands or genitals. These areas may develop a swelling that is frightening in appearance but usually goes away in less than 24 hours. This swelling is called angioedema.
In many cases, a single attack of hives is due to an infection or virus and these go away within a few days to a few weeks. Some people get repeated attacks that occur as an allergic reaction to a variety of things (foods, most commonly nuts, chocolate, fish, tomatoes, eggs, fresh berries and milk, insect stings, and medications). In this case, they usually break out within a few hours of exposure. Usually, the patients figure out the cause by themselves, and they never bother coming to a doctor.
Occasionally, a person will continue to have hives for many years. These hives, called chronic urticaria, can be one of the most frustrating problems dermatologists see in their patients. This is defined as hives lasting longer than 6 weeks. Patients like this come in miserable and worried about this problem, often having seen multiple specialists. Neither the patient nor the doctor can determine the cause of the hives. Patients will often say, “It has got to be something causing these hives.” The truth is hard to accept for some patients.
Treatment may not be needed if the hives are mild. They may disappear on their own. To reduce itching and swelling, the physicians recommend: Avoid hot baths or showers. Avoid irritating the area with tight-fitting clothing. Apply calamine lotion. Take antihistamines – The most well tolerated initial treatment is the non-sedating antihistamine Claritin. Zyrtec is similar but may sometimes cause sedation. If that doesn’t eliminate the hives, a sedating-type of antihistamine (hydroxyzine, cyproheptadine or doxepin) is added at night. A short course of oral cortisone can often help to clear the hives completely if the above measures are ineffective.
In the overwhelming majority of cases of chronic hives (95%), the cause is considered “idiopathic” (a medical term that means there is no discernible cause). Because of that 5 % of cases with a cause, it is worthwhile for to determine if any underlying disease is present (e.g. thyroid problems, liver problems, skin diseases, sinusitis) or if there is an allergic cause (i.e. a reaction to a drug, insect, food, etc.). This can be accomplished by a good history and physical, a few types of blood and urine tests, a skin biopsy, and at times Patch Testing (see Contact Dermatitis). Some patients with chronic hives and elevated anti-thyroid antibodies in the blood improve when given a thyroid supplement even if the thyroid function is normal.