Corns and calluses are usually caused by shoes that are too tightly fitting. Therefor they press on the same spot at the feet (toe or sole) continuously for a long time. The longer the pressure on the foot lasts, the thicker the skin underneath becomes and thus the pressure increases again. This causes the skin to keratinize not only upwards but also downwards and hurts. This pain is caused by a corneal cone which hits the nerves in the depth of the skin and irritates it. The cause of corns is not only shoes that are too tight, but also defective positions of the foot and other orthopaedic problems.