People with diabetes face special skin challenges. Because diabetes affects the capillaries, the small vessels which feed the skin its blood supply, thickening of the skin increases the difficulty to supply nutrients to the skin.
Additionally, the shear and pressure forces that cause corns and calluses may tear the capillaries, causing bleeding within the callus or corn.
Often, bleeding within the calluses is an early sign of diabetes, even before elevated blood sugars. 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 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.