Over years, the field of medicine has been able to determine what some of the common causes of hives or urticaria are. It is important to note that many of these factors do not ordinarily provoke hives in most people. Hence, it is implied that the people who develop hives when exposed to them are often already hypersensitized.

This article does not look into what causes the hypersensitization in the first place but, rather, at the factors that trigger the hypersensitized person to develop hives. The factors in question vary significantly, but they ultimately provoke similar processes within the body: they trigger the release of the chemical histamine in the skin by special cells called mast cells. This, in turn, causes plasma to leak from the tiny blood vessels nearby, resulting in the development of the characteristic swelling in the skin.

Common Causes of Hives and the Associated Varieties of Urticaria

Each of the common causes of hives is typically associated with a particular variety of hives or urticaria. Acute urticaria, named thus because it lasts less than 6 weeks, typically develops as a response to various substances, including foods, medicines and the toxins from insect bites. Some infections, for instance underlying viral infections, also trigger acute urticaria.

Fresh foods like milk, nuts, shellfish, eggs, berries and tomatoes are common causes of hives in those who are allergic to them. Cooked foods do the same to a lesser extent. Processed food products, including chocolate, preservatives and additives can also trigger hives. As for medications, these can also trigger hives when they are relatively new additions to the patient’s regimen. They are typically medications that provoke the mast cells to release histamine. Examples include ACE inhibitors (for high blood pressure), non-steroidal anti-inflammatory drugs (like ibuprofen, aspirin and naproxen) and opiates (like codeine and morphine).

Chronic urticaria, which lasts longer than 6 weeks, is mostly “idiopathic”. This is to say medical practitioners are unable to determine what caused it even after they have considered all the common causes of hives to which the patient has been exposed. Sometimes they eventually determine the cause. When that happens, the urticaria can no longer be considered idiopathic. In a minority of cases, chronic urticaria has readily determinable causes. These include cases of physical urticaria, which is triggered by physical stimuli like pressure, water, cold, sweat, heat, sunlight and exercise. Dermatographism is the form of physical urticaria that results wherever one exerts pressure on the skin.