The high level of blood glucose found in diabetics can cause nerve damage and poor blood flow, which in turn can lead to serious foot problems such as foot ulcers or foot sores. You may not feel a cut, a blister or a sore because of nerve damage. Damage to the blood vessels can also mean that your feet do not get enough blood and oxygen making it harder for your foot to heal if you do get a sore or infection.
Click here for more information. http://www.nlm.nih.gov/medlineplus/diabeticfoot.html