Seborrheic keratoses are benign (noncancerous) skin growths that develop from skin cells called keratinocytes. These growths have a waxy or greasy look and can be tan, brown or black. They look like they have been glued or stuck onto the skin. Over time, the growths become rough and crusty looking.
Seborrheic keratoses usually appear alone, but others may develop. They usually are found on the chest and back but can appear anywhere on the body, including the face, scalp and neck.
No one knows what causes seborrheic keratoses, but they become more common with age. Most people will develop some seborrheic keratoses as they get older, and children rarely have them. Seborrheic keratoses are not contagious.