Welts are bumps in the skin that are caused by a fluid buildup directly below the surface of the skin. A number of things can lead to the development of a welt, ranging from trauma to the skin to an allergic reaction. Depending on the cause, a welt may be a sign of a serious problem, or it may be something which will resolve on its own, given enough time. When welts are a sign of a medical problem, they are usually accompanied by other symptoms which provide clues to the problem.

Physical trauma such as a blow can cause a welt, and welts can also be caused by allergic reactions, infections, injections, insect bites, and skin reactions, in very sensitive people. For example, in people with dermographism, even a gentle touch to the skin can cause a welt to emerge. The welt is typically pale red, although welts may have a whitened area in the center, and some are surrounded by a streak of reddish or unusually pale skin.

Left to its own devices, a welt will gradually subside as the fluid is reabsorbed by the surrounding cells. However, when a welt is a sign of an allergic reaction or infection, it can get worse, or it can indicate that the welt's owner requires some medical treatment. For example, welts characterize the itchy rash known as hives which emerges when people experience severe allergic reactions. The appearance of hives can be a sign of anaphylactic shock, a medical condition which can be deadly if left untreated.

For people with sensitive skin, welts may be a common experience, and nothing to worry about. However, if welts appear unusually large or they appear to be spreading, getting medical attention can be advisable. A doctor can determine the cause of the welt and the best course of action, ranging from topical skin creams to soothe irritation to the provision of steroids and other aggressive anti-allergy treatments.

You may also hear a welt referred to as a wheal. Welts are often tender to the touch, because the area is inflamed and irritated, and sometimes they feel hot. Wearing tight clothing against a welt is usually ill-advised, because the garment can scratch and irritate the welt, causing it to swell and spread. Sometimes, applying ice or an astringent like witch hazel to a welt can soothe the itching and burning associated with welts.