There are many causes of urticaria, and include allergens, skin and sensory sensitivities, and other rare causes. Urticaria are hives, which are red, raised areas of skin that may itch. When an allergen is presented in the body, mast cells produce histamine, which is then released into the surrounding tissues. The histamine causes nearby blood vessels to leak fluid, resulting in localized swelling and redness. Pain and itching are caused by the irritation of nerve cells by the release of the histamine.
Hives can range in size from tiny raised bumps to large patches that spread around the body. They can be bright red or a light pinkish color. The reddened areas will blanche, or turn white when touched. An acute case of hives can last anywhere from a few hours to a few days. Any instance of hives that lasts longer than six weeks is known as chronic urticaria.
There are many different types of allergens which are known causes of urticaria. These include food, medications, bee stings, insect bites, and animal dander. It is possible for a person to experience a severe reaction, even if he has never been exposed to the allergen or had a similar reaction before. If urticaria develops, the patient should be closely monitored for signs of anaphylaxis.
An anaphylaxis reaction means that hives have developed internally, often in the oral or throat region. This can lead to severe breathing difficulties. Urticaria is often the first sign of an anaphylactic reaction. Many people who have known allergens and have experienced severe reactions in the past carry a syringe and doses of epinephrine, which can be injected to counteract the histamines in the patient. If a person has both signs of urticaria and complains of shortness of breath, he should be brought to an emergency room for monitoring and treatment.
Skin and other sensory sensitivities are also causes of urticaria. These include sensitivities to sunlight, water, changes in temperature, or when pressure is applied to the skin, such as when wearing too tight clothes. Reactions to synthetic materials in perfumes, deodorant, and detergents can also increase the production of histamine, resulting in an outbreak of hives. Most of these urticaria cases can be reduced by changing products and clothing, as well as being mindful of light and temperature.
Other causes of urticaria are harder to determine. Some people develop hives during times of excessive stress or excitement. Urticaria can also be a symptom of an auto-immune disease, such as lupus. Often, the urticaria trigger is never identified, and is labeled idiopathic.