A callus presents as a broad-based diffuse area of hard growth with relatively even thickness and it lacks a distinct border. The affected skin is rough and discoloured, varying in colour from white to grey-yellow or brown. They usually develop at the ball of the foot or around the heel area, but they can also be found on the palm of the hands or the knuckles.
Callus may also be spelled callous. A callus is sometimes referred to as callosity or tyloma in dermatology. A callus is a small area of thickened skin. The formation is caused by continued friction, pressure, or other physical or chemical irritation. Calluses form as result of a mild repetitive injury causing increased activity of the cell growth of the epidermis (the outermost layer of the skin). This gives the skin a local rise of increased tissue. Resulting in a hardened thickened pad of dead skin cells at the surface layer of the skin. Callus serves to protect underlying tissues.
Callus can form over any bony prominence. Calluses are most frequently seen on the hands and feet. The ball of the foot, the heel, and the underside of the big toe are commonly affected. However, they can occur anywhere. Callus can be annoying, but your body actually forms them to protect sensitive skin. Although calluses are typically benign, pressure or friction can precipitate pain. For foot calluses specifically, thin-soled and high-heeled shoes amplify discomfort. Relief comes with rest. Calluses are more common in women than men.
Calluses are often painless and can actually be advantageous to some athletes. Boxers and martial artists, for example, build up calluses on their hands to become more resistant to pain from impact. Dancers find that calluses can facilitate their performance of turns.
Corns and calluses are often confused with one another. Calluses are generally thickened flat discoloured areas of the skin and most of the time painless. However they can result in pain, discomfort, and disfigurement. Especially when a callus is conical in shape, penetrating into the deeper layer of the skin and causing pain when pressed. Such a callosity is called a corn. Corns are small circles of thick skin that usually develop on the tops and sides of toes or on the sole of the foot. Calluses are larger than corns and don't have such a well-defined edge.
A wide variety of extrinsic and intrinsic factors may lead to the development of a callus. Extrinsic factors have to do with skin rubbing against something, such as a bone, a shoe or the ground. For example poorly fitting footwear. Shoes that are too small or tight or have a small toe box can be a cause of forming callus. Also, walking barefoot, wearing thin-soled shoes, wearing high heels, wearing thick socks or socks with seams by the toes. Another cause of forming callus is prolonged and repetitive standing. Also regularly holding objects such as a hammer or racquet. Athletes develop calluses from repetitive motion and recurrent pressure on the same spot.
Intrinsic factors that may lead to the formation of calluses include poor foot mechanics or abnormal gait, obesity, dry skin, reduced fatty padding (elderly people have les fatty tissue in their skin) and a variety of foot deformities. As callused skin is thick, it's often less sensitive to touch than the surrounding skin.
Most calluses are harmless and do not require diagnosis or treatment, but some prompt affected individuals have to seek medical attention. Calluses are diagnosed based on findings from a clinical exam. The location and characteristics of the lesion are noted, and the affected area is palpated to feel for a prominent bone underneath the skin surface. X-rays may be used to examine the underlying bone structure in order to determine whether it is the cause of a callus.
Clinicians assess the area for any contributing factors, such as footwear, repetitive activities, medical history, and previous surgery. Foot mechanics may be evaluated by observing a patient’s gait. Identification of an underlying source of increased mechanical stress on the affected body part can influence the course of care and treatment for a callus.
Calluses that develop on the weight-bearing portion of the forefoot and that become extremely painful may be diagnosed as intractable plantar keratosis. In some patients, pain is focused at the central core of a single callus, whereas in others the pain is more diffuse across the weight-bearing portion of the forefoot. Other conditions that can resemble calluses include warts, tumours of the skin and subcutaneous tissues, and a reaction to a foreign object embedded in the skin (e.g., a wood sliver or a piece of glass). Genetic and metabolic disorders of the skin can also cause skin thickening, which can be mistaken for a callus.