Physical forces agents may induce distinctive skin changes. Pressure and friction induce callus and corn. Callus and corn arise at sites of friction or pressure, particularly palms and soles, and especially the bony prominences of the joints. Pressure, shearing forces, friction, and moisture are main etiologic factors of pressure ulcer. The pressure ulcer is caused by ischemia of the underlying structures of the skin, fat, and muscles. Skin has long been known to be a very radiosensitive organ. Skin changes after radiation exposure follow a predictable course dictated by radiation dose, timing, and the biology of the human inflammatory reaction. When the skin is exposed to radiation, acute radiation dermatitis, chronic radiation dermatitis, skin cancer, and radiation recall dermatitis may be developed.