A build up of callus usually occurs in areas of extreme friction and pressure, such as the bony areas on the ball of the foot, the rim of the heel, the underside of the big toe and the outer side of the little toe.  Callus is incapable of bending and stretching like normal skin and that is why we get cracked heels, particularly when wearing flip flop style shoes in the summer months. The constant slapping movement upon the skin will stimulate the formation of callus.

Calluses appear naturally to protect the feet of people who frequently walk barefoot on rough surfaces, but if calluses develop whilst you are wearing shoes, they could be a sign of some structural imbalance.  Calluses can often indicate incorrect weight distribution. for instance  High heeled shoes puts all the weight on the ball of the foot which tends to causes calluses in that area.  

Calluses can put pressure on the nerve and blood vessels beneath it and when walked upon they are pressed back into the plantar surface, causing discomfort and pain.

Callus can be treated by debriding the skin to reduce the callus and using emollient preparations to maintain suppleness and prevent drying out.

Appropriate management of callus is crucial in patients with diabetes.  Callus needs to be removed frequently as it can build up quickly and this could cause ulceration especially if the diabetic patient has peripheral neuropathy (loss of sensation in the feet). 

Reduction of callus in the diabetic patient requires delicate care to avoid the risk of injury and infection.