Corns and calluses are areas of thick, hardened, accumulated dead skin cells that are caused by repeated rubbing, friction, or pressure. They can form anywhere on the body but are most commonly found on the hands, toes, heels, or soles of the feet.
Both are the result of hyperkeratinization—the thickening of the top layer of skin, known as the stratum corneum.1 If your shoe repeatedly rubs against a spot on your foot, for example, the inflammation and gradual build-up of scar tissue lead to the development of a corn or callus.
While we tend to think of corns and calluses as interchangeable, they are distinctive in their appearance, causes, and sensitivity.
Corns are small, defined areas of thickened skin that usually form on bony areas of the foot, such as the joints of toes. They most commonly develop where the skin is thin and glabrous (hairless and smooth).
Corns differ from calluses in that they have a hard core surrounded by inflamed skin. Because their shape is typically well defined, they can often be mistaken for warts.
As with a wart, a corn is typically hardened and raised with a flaky, dry, or waxy surface. However, corns can be differentiated by their location on the top of the foot and between toes rather than the bottom (plantar) side of the foot. Warts can also appear in clusters, which corns generally don't, and develop on any part of the body.
There are both soft corns and hard corns. Soft corns develop on the moist skin between toes in response to abnormal friction (such as walking in tight, pointed-toe shoes). They tend to be whitish in color with a rubbery, pliable texture.
Hard corns, by contrast, develop on dry, flat areas of skin, especially bony parts of the foot that are tightly compressed in shoes. Hard corns form where a bone comes into direct contact with the inside of a shoe (especially shoes in which the toes are abnormally curled). They tend to be small and circular and co-exist with calluses.
Within both soft and hard corns is a barley-shape core that runs perpendicular to the foot from the top of the corn to the tissues below. Because of its shape and position, the hardened core can sometimes press on nerve endings, causing sharp, stabbing pain.
There are also tiny "seed corns" that commonly develop on the ball of the foot and, despite their diminutive size, are no less painful.
Calluses are less-defined patches of thickened skin. Typically larger than corns and rarely painful, they are caused by friction or pressure delivered over a long period of time. Even writing with a pencil over the course of years, for example, can lead to the development of a callus on the middle finger of the writing hand.
Calluses are usually not painful and tend to involve larger areas of skin, especially under the heels or on the palm, knees, or balls of the feet. The skin can sometimes be smooth and hard or rough, dry, and patchy.
Among some of the situations that cause calluses:
Playing on monkey bars
Playing sports with equipment that has handles (such as tennis or golf)
Strumming or plucking guitar strings
Wearing high heels
A callus may be considered a form of protection in that the layers of dead skin cells are resistant to blisters and friction.
The only time a callus causes pain is when it cracks and exposes the underlying tissue. This is not uncommon with heel calluses in which the thick layers of skin are less able to flex. Once a crevasse forms, it can make walking difficult; any additional pressure placed on the heel can increase the size and depth of the crack.
Most corns and calluses do not require medical treatment and can be treated at home with proper foot care and simple, over-the-counter products.
To treat a callus or corn safely:
Remove the source of the irritation. This may require you to wear different shoes or to replace those that are too tight or loose, for example. This is especially true as your feet age and begin to experience changes in the arches or thickness of the skin.
In some cases, orthopedic shoes or orthotic insoles may be needed to compensate for any abnormalities in the structure of your foot and/or gait. A foot analysis also can help.
Soak your foot or hand in warm water. Doing so for 10 to 20 minutes can soften the skin and may help relieve some of the pain. Once finished, dry thoroughly.
Abrade the skin with a pumice stone. This is something you need to do gently, generally on larger patches of thick skin. Soaking your skin beforehand makes the exfoliation much easier. Once completed, use an extra-thick, emollient-rich lotion or cream to lock in the moisture and keep the skin soft.
Pad the callus or corn. The best way to deal with pain and promote healing is to pad the affected area of skin.2 Adhesive corn patches and elastic toe sleeves can be readily found at most drugstores.
To protect larger areas of skin, ask your pharmacist about gel insoles or heel cups. If the callus or corn is on your hand, cover it with a bandage strip and wear protective gloves while working.
There is also a wide variety of over-the-counter corn removers that typically contain salicylic acid. While they can be effective in removing a corn, discontinue use if you experience any pain or skin irritation.
You should avoid these products if you have diabetic neuropathy or any condition that affects the blood flow to the foot (such as peripheral arterial disease).3 Conditions like these can impede normal healing and lead to the development of sores and ulcers that are hard to treat.
If you have diabetes, peripheral neuropathy (foot nerve pain), leg edema (fluid overload of the feet and ankles), or any chronic circulation problem, do not attempt to self-treat your corns or calluses. Always see a doctor.
When to See a Doctor
If a corn or callus is painful or bleeding, you should have it looked at by a podiatrist. Pain or bleeding is an indication that the deeper layers of skin are being affected. Ignoring these symptoms may result in otherwise avoidable complications, such as infection or ulcerations.
Treatment may involve debridement (the removal of damaged tissue) or the paring (cutting out) of a corn with a scalpel.
It is important to note that corns and calluses will often return even after effective treatment. If they become problematic, surgery may be explored (especially for corns). This should only be considered if all other conservative forms of treatment have failed to provide relief.
In such a case, surgical enucleation (the removal of the hardened core), bunionectomy (removal of a bunion), or even foot alignment surgery may be considered.