A callus is an especially toughened area of skin which has become relatively thick and hard in response to repeated friction, pressure, or other irritation. Rubbing that is too frequent or forceful will cause blisters rather than allow calluses to form. Since repeated contact is required, calluses are most often found on feet because of frequent walking. Calluses are generally not harmful, but may sometimes lead to other problems, such as skin ulceration or infection.

People with diabetes face special skin challenges. Because diabetes affects the capillaries, the small blood vessels which feed the skin, thickening of the skin with callus increases the difficulty of supplying nutrients to the skin. Callus formation is seen in high numbers of patients with diabetes and together with absent foot pulses and formation of hammer toe, [1][2] this may be an early signs of individuals at an increased risk for foot ulcers.[1]

The stiffness of a callus or corn, coupled with the shear and pressure that caused it, may tear the capillaries or adjoining tissue, causing bleeding within the callus or corn. Often, bleeding within a callus is an early sign of diabetes, even before elevated blood sugars may be noticed. Although the bleeding can be small, sometimes small pools of blood or hematoma are formed. The blood itself is an irritant, a foreign body within the callus that makes the area burn or itch. If the pool of blood is exposed to the outside, infection may follow. Infection may also lead to ulceration. Luckily, this process can be prevented at several places, but such infections can become life-threatening. Diabetic foot infections are the leading cause of diabetic limb amputation.

If you are diabetic and suffer from foot calluses, diabetic shoes can help reduce the risks associated with your feet. Proper fitting footwear has been shown to help reduce the chance of diabetic foot ulcers in patients with callus formation. Click here to see how diabetic shoes can help you:  Diabetic Shoes

1. ¹^ ^{a b} Alavi A, Sanjari M, Haghdoost A, Sibbald RG (April 2009). "Common foot examination features of 247 Iranian patients with diabetes". Int Wound J 6 (2): 117–22. doi:10.1111/j.1742-481X.2009.00583.x. PMID 19432661.  -12% having callus formation
2. ²^ Tantisiriwat N, Janchai S (July 2008). "Common foot problems in diabetic foot clinic". J Med Assoc Thai 91 (7): 1097–101. PMID 18839852.  -56% having callus present