Originally published by Harvard Health.
What Is It?
Corns and calluses are a thickening of the outer layer of skin. This thickening is known medically as hyperkeratosis. Corns and calluses develop as part of the skin’s normal defense against prolonged rubbing, pressure and other forms of local irritation.
- Corns — A corn is a protective thickening of the skin on a bony, knobby portion of a toe. At the center of a corn is often a very dense knot of skin called a core, which is located over the area of greatest friction or pressure.Firm, dry corns that form on the upper surfaces of the toes are called hard corns. Pliable, moist corns that form between the toes are called soft corns. In most cases, corns develop when the foot has been squeezed into a shoe that has a very narrow toe area. Less often, corns develop on deformed toes that cannot fit comfortably into regular shoes.
- Calluses — A callus is a thickening of skin that is exposed to prolonged rubbing. Unlike a corn, the thickening in a callus is evenly distributed. There is no dense central core. Although calluses usually occur on the soles of the feet, they also can form on other parts of the body that are exposed to long-term friction. For example, calluses often are found on the hands of manual laborers, guitar players, gymnasts, weight lifters, tennis players and other people who routinely handle tools, instruments or sports equipment. Calluses can be a physical advantage — for example, among laborers and athletes — because they cushion the hands and allow the person to function without pain.On the soles of the feet, calluses typically develop near the base of the toes, where they are caused by friction from the inside of shoes. Less often, calluses are related to walking problems or foot abnormalities that place unusual stress on parts of the foot during walking.
According to the American Podiatric Medical Association, painful corns and calluses affect about 5% of people in the United States every year, and many people never seek professional help.
On the feet, a small corn or callus may not cause any symptoms. However, a large, bulky corn or callus can cause foot pain and difficulty walking.
After prolonged irritation, a discolored area (brown, red or black) may develop under a large corn or callus. This discoloration is caused by a small amount of bleeding in the space between thick and normal skin. In severe cases, the thick and normal skin may separate, exposing the area to possible infection, especially in people with diabetes.
Your health care professional probably will ask about your shoes, because shoes with narrow toes are more likely to cause corns. He or she also will ask about your foot history and your history of other medical problems, including diabetes and circulation problems. Some types of foot problems can alter the mechanics of the foot, causing abnormal pressure on certain areas and leading to calluses. Also, any previous surgery or trauma to the feet may affect the structure and alignment of foot bones, increasing the risk of calluses.
To assess whether your corns and calluses are related to foot abnormalities, your doctor will inspect your feet for toe deformities, structural problems of the bones, poor bone alignment and problems related to an abnormal way of walking (gait). If your doctor finds some abnormality during this part of the foot exam, he or she may suggest a specific type of padding or shoe insert to help prevent your corns and calluses from returning or causing as much discomfort.
Also, whenever there is a painful area of thickened skin on your feet, your doctor may need to check whether it is a plantar wart, a localized skin infection caused by human papilloma virus. The diagnosis can be made by shaving down the thickened skin and looking for tiny blood vessels at the base and a lack of normal skin ridges (as in a fingerprint), the hallmarks of a plantar wart.
Corns and calluses can be long-term problems if you consistently wear shoes that do not fit properly. Even with good footwear, you may continue to have painful corns and calluses if there is some abnormality in your gait or foot structure that causes unusual stress on parts of your feet when you walk.
In most cases, you can help to prevent corns and calluses by wearing shoes that fit properly. In particular, choose low-heeled, comfortable shoes that have enough space around the toes. Wear socks to cushion any areas of unusual rubbing or pressure, and use foot powder to reduce friction.
If your corns and calluses are painful, your doctor may shave away some of the thickened skin to relieve pain and pressure in the affected area. Although many people can do this themselves, podiatrists and other foot specialists can make sure the procedure is done safely. Your doctor also may recommend that you modify your footwear to prevent your problem from returning. For example, pads or “donuts” made of moleskin, lamb’s wool, foam or felt will cushion the affected area. Corrective shoe inserts will redistribute the forces that cause friction and pressure inside your shoes, relieving some of the stress on your feet when you walk.
Your doctor may ask you to return regularly to have your feet examined and your corns and calluses shaved, if necessary.
You also can minimize corns and calluses by regularly rubbing them with a pumice stone, which is available in most drug stores.
After the corn or callus is shaved down, application of salicylic acid plasters or pads (available over-the-counter) can be helpful. However, this treatment should not be used by people with nerve disease (neuropathy) or circulation problems in the feet.
In rare cases, foot surgery may be necessary to treat corns and calluses that keep returning and are not relieved by padding, shoe inserts and periodic shaving. Never try to shave or cut a corn or callus on your own. Instead, use a pumice stone to trim it down safely.
When To Call a Professional
Make an appointment to see your family doctor, orthopedic surgeon or podiatrist if you have painful corns or calluses.
If you have diabetes or poor circulation, examine your feet every day. For the best view, use a mirror to inspect the soles of your feet and the skin folds between your toes. If you see an area of redness, swelling, bleeding, blisters or any other problem, call your doctor promptly.
Although corns and calluses tend to return even if they are removed, this may be less likely if you use foot padding and shoe inserts.
American Orthopaedic Foot and Ankle Society
2517 Eastlake Ave. E
Seattle, WA 98102
American Podiatric Medical Association (APMA)
9312 Old Georgetown Road
Bethesda, MD 20814
American College of Foot and Ankle Surgeons
8725 West Higgins Road
Chicago, IL 60031-2724