Keratosis of the skin refers to two different types of noncancerous skin growths: seborrheic keratosis and actinic keratosis.

Seborrheic keratosis is a common benign skin growth that appears gradually, usually on the face, neck, chest, or back. It is usually brown, black, or light tan, and looks waxy or scaly and slightly raised. Seborrheic keratoses are harmless and not contagious, and they dont need treatment. However, they can be removed if they become irritated by clothing or if the person doesnt like how they look.

Actinic keratosis is a rough, scaly patch on the skin that develops from years of sun exposure. Its often found on the face, lips, ears, forearms, scalp, neck, or back of the hands. Actinic keratoses are not cancerous, but they can turn into a type of skin cancer called squamous cell carcinoma if left untreated. Symptoms include rough, dry or scaly patch of skin, usually less than 1 inch (2.5 centimeters) in diameter, flat to slightly raised patch or bump on the top layer of skin, and color variations, including pink, red, or brown. Itching, burning, bleeding, or crusting may also occur.

The causes of seborrheic keratosis and actinic keratosis are not fully understood, but they tend to run in families, so there is likely an inherited tendency. Sun exposure is also a risk factor for actinic keratosis.