A corn is a small round area of skin that has become hardened because of pressure or friction. It can push inwards into deeper layers of skin which makes it painful.
Hard corns generally form on the tops of toes or edges of outer edge of the little toe. They are yellow in colour.
Soft corns sometimes form between toes and stay soft due to sweat. They tend to be paler yellow or white and can get infected.
Seed corns are little seed-sized bumps that can develop on the ball of the foot or the bottom of the heel. You may get just 1 or a cluster of them. They can be painless or painful.
A callus is a larger area with a less well-defined edge. They tend to form on your hands or under your foot, typically just behind your toes, where you put walking pressure on the bones. They are not usually painful.
Calluses and corns are not caused by a virus and are not contagious (not passed from person to person).
Image credit: Canva
Calluses on the hand
Calluses on the hand are caused by constant handling of an object that causes friction and puts pressure on the hand. This includes playing instruments, handling tools (gardening hoe or hammer), using your hands in sports such as rock climbing, or using sports equipment (eg, tennis racquet).
Calluses and corns on the feet
Walking barefoot outside or wearing shoes without socks can cause calluses. Also, calluses and corns may be caused by friction or pressure from:
Wearing tight shoes and high heels which can compress areas of your foot. When footwear is too loose, your foot may repeatedly slide and rub against the shoe. Your foot may also rub against a seam or stitch inside the shoe.
Sports (such as a callus forming on the bottom of a runner's foot) or an odd way of walking
Particular bone structure such as flat feet or bone spurs (small, bony growths that form along joints). Calluses and corns often form on bunions, hammer, claw, or mallet toes, or on the bumps caused by rheumatoid arthritis.
Pumice stone or emery boards
Calluses or corns that cause mild discomfort and are not red, swollen or painful, may be rubbed down with a pumice stone or emery board. Many people can do this themselves. It is best to soak your foot in warm water for 20 minutes to soften the thick skin before using a pumice stone or emery board. Afterwards, use a moisturising cream to keep the skin soft. Some people find it useful to wear gloves at night after applying the cream.
Trimming (also called paring)
Trimming of a corn or callus must be done by a trained person qualified to treat foot disorders (a podiatrist). The hard, thick skin of a corn or callus is trimmed down using a scalpel blade. This reduces the pain caused by the corn or callus. Sometimes, repeated or regular trimming sessions are needed. Once a corn or callus has been pared down, wearing good-fitting footwear may prevent it from returning.
Medicated creams, pads, drops or patches to treat corns and calluses can be bought from the pharmacy. These usually contain a chemical called salicylic acid. Salicylic acid is a keratolytic (which means it dissolves the thick layer of dead skin). It is important to use these products as directed in the package instructions; these products are gentle and safe for most people. You should use petroleum jelly or a plaster to protect the skin around the corn or callus.
These products should not be used if you have diabetes, poor circulation . This is because your skin is less likely to heal well after using salicyclic acid and there is a risk that an ulcer may develop.
Corn plasters can help to relieve discomfort but will not treat the corn.
Sometimes pieces of protruding (sticking out) bone need to be surgically removed. Your doctor will refer you to an orthopaedic surgeon if this is needed.
Video: How to treat corns and calluses
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(American Academy of Dermatology, US, 2016)
Note: This video is from overseas so some details may be different in New Zealand, eg, phone 111 for emergencies or, if it’s not an emergency, freephone Healthline 0800 611 116.
What happens if a corn becomes infected?
If your corn gets more painful, and especially if it has a reddened area around it and/or you see pus coming out if it talk to your doctor. You may need antibiotics.
In some people, calluses and corns can be prevented by reducing or eliminating pressure and friction on the skin and keeping the skin soft, using simple measures such as:
Wearing gloves to protect your hands, such as when gardening or lifting weights.
Wearing shoes and socks that fit well and have a wider toe box. If you have hammer or claw toes extra height is needed in your shoes. A podiatrist can advise on appropriate footwear if you have unusually shaped feet.
Applying a non-medicated pad or inner-sole to protect the areas of your feet that are exposed to friction. These can be bought from your pharmacy.
If you have toes that rub together they can be kept apart with lamb’s wool or soft cotton. Toe separators are also available to space your toes out, talk to a podiatrist about this.
Soaking your hands or feet, and apply moisturizer to help keep the skin of your hands and feet soft.
The way you walk can be affected by the bones in your feet or even tight calf muscles. This may lead to foot problems such as calluses and corns. A podiatrist may be able to help you make changes that can prevent these problems.