Urticaria, also known as hives, is characterized by red, raised itchy welts (wheals) of varying sizes on the surface of the skin. The small bumps may look similar to mosquito bites, and they tend to occur in clusters. Hives are among the most common symptoms of an allergic reaction.
The lesions of hives are caused by inflammation in the skin. Many allergens, including foods and medications, trigger allergic reactions that cause urticaria. Hives appear after the body releases histamine, triggering an allergic reaction. Researchers estimate that 15-20% of Americans experience hives as part of an allergic reaction. Medical conditions including autoimmune disorders, infections, and physical factors may cause hives.
In most cases, hives are harmless and do not leave any lasting marks, even without treatment. However, caution is advised because an allergic reaction can progress into more serious symptoms like difficulty breathing. Also, once a person is sensitized, the reaction may be worse on subsequent exposure to an allergen.
Treatment varies depending on the underlying cause and severity of the symptoms. Allergy medications may include antihistamines or leukotriene receptor antagonists. Intravenous immune globulin (IVIG), made of antibodies extracted from pooled blood donations from hundreds to thousands of donors, may help treat autoimmune disorders and allergen immunotherapy (allergy shots) may help reduce the body's sensitivity to certain substances.
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urticaria and angioedema
Urticaria (hives) and angioedema are different manifestations of the same pathologic process. In both conditions, the small veins in the body become swollen, causing fluid leakage and edema (swelling). However, urticaria is localized to the superficial portion of the dermis layer of the skin, while angioedema involves vessels in the layers of the skin below the dermis.
Urticaria is characterized by round wheals with raised, swollen, red edges, and a central blanching (whitening). Because angioedema occurs below the skin, it causes well-demarcated, localized, non-pitting edema. Pitting edema occurs when a bump on the skin is pressed down and it remains indented for a certain length of time.
Urticaria and angioedema can occur together or separately. Recurrent episodes of one or both conditions for less than six weeks are considered acute, whereas longer-lasting outbreaks are considered chronic.
types of urticaria
Ordinary urticaria: Ordinary urticaria can be caused by exposure to an allergen, or the cause may be unknown. It is the most common form of urticaria. This form can be either acute or chronic. Acute ordinary urticaria typically only lasts a few days. Infections (like the flu) or allergic reactions to substances such as food or medicine may lead to acute urticaria. Chronic urticaria lasts for more than six weeks and the cause is often unknown.
Physical urticaria: Sunlight, heat, cold, water, pressure, vibrations, or exercise may cause what is known as physical urticaria. Solar urticaria (in response to sunlight) forms within minutes of sun exposure and typically fades after one to two hours. Cold urticaria appears when the skin is warmed after exposure to cold.
Dermatographic urticaria: Dermatographic urticaria forms after the skin has been firmly stroked or scratched. This form can often occur with other types of urticaria and may last for months or even years. Most patients with dermatographic urticaria are otherwise healthy.