An actinic keratosis (AK) is a flat, scaly growth on the skin that usually forms on parts of the body that are exposed to direct sunlight. AKs can be any shape and are skin-colored, reddish-brown, or yellowish-black in color. They range in size from as small as a pinhead to more than an inch across. The surface of the AK is dry and rough to the touch. Occasionally, an AK may itch or feel prickly, especially after sun exposure.

AKs are most commonly found in fair-skinned people who have spent a lot of time in the sun. If AKs are not treated, 10% to 15% may develop into a form of skin cancer called squamous cell cancer.

Examples of AKs: