What Is It?
Hyperkeratosis is a thickening of the outer layer of the skin. This outer layer contains a tough, protective protein called keratin.
This skin thickening is often part of the skin's normal protection against rubbing, pressure and other forms of local irritation. It causes calluses and corns on hands and feet. It can cause whitish areas inside the mouth.
Other forms of hyperkeratosis can occur as part of the skin's defense against: