Seborrheic keratosis on the scalp of a 49 year old female patient. This skin growth is caused by over-production of keratin, the tough fibrous protein found in hair and the outer layer of skin. Keratoses range from flat, dark brown rough patches to small, wart-like protrusions covered with a greasy, removable crust. They are harmless and are not contagious. Those over 50 years old and with a family history of the condition are at more at risk for developing seborrheic keratosis. They can be removed by cryosurgery (destruction of tissue using extreme cold) or surgical excision.