While corns rarely cause serious problems, they can cause pain and irritation to runners. A corn is an area of thickened skin that becomes inflamed. Poorly-fitting shoes are often implicated as the cause, and the American Academy of Sports Medicine asserts that 85 percent of the public wears shoes that are too small.

According to the "New York Times" Health Guide, a corn is actually a protective mechanism, although runners often feel they need protection from the corn. Pressure or friction causes skin to form a layer of dead skin cells in a small area. Corns often look cone-shaped with a rounded core that can cause pain. Soft corns, found in moist areas, can peel.

Several causes of corns exist. Since toes are the area often affected by corns, situations that cause pressure on the toes are to blame. Shoes or socks that fit too tight as well as shoes that fit too loose cause corns. Loose shoes increase friction, particularly when running. If your toes are unusually shaped and rub together, you are at risk for corns.

DermNet NZ recommends reducing pressure and thickness of skin to treat corns. A corn cushion can be used to distribute pressure evenly for areas on the side of the foot when running. For corns in between the toes, try separating toes with cotton or lambswool. To reduce the skin thickness, soak the affected area to soften it. Gently use a pumice stone on the surface of the corn. There are specially-designed corn trimmers that may be helpful. Since running puts extra stress on feet, frequent runners should see a podiatrist for corn removal.

With extra pressure and friction on their feet, properly fitting shoes become a key corn prevention tool for runners. The American College of Sports Medicine offers the following tips to keep in mind when purchasing running shoes. Look for shoes that have half an inch of room between the longest toe and the top of the shoe. The shoes should also be wide enough, with the fit not tight, but also not allowing for much movement of the foot. Try the shoes late in the day with the same socks you will run in. Keep the shoes on for at least 10 minutes to assess the fit. Break in the new shoes in short running sessions.