Seborrhoeic keratosis is caused by excessive growth of the top layer of epidermis. It is related to skin aging and sun exposure, is usually found in people over 30 years old, and tends to become more common and more numerous with age.

It is commonly seen on the face and scalp, but also often found on the chest and back. It can be solitary or in clusters. It appears as a lump of light tan to black colour, with sizes range from a few mm to a few cm, and has a look of a rough lump being stuck onto the surface.

It is unsightly, especially when appearing on the face, and in a cluster of numerous lumps. It can get irritated by friction and scratching. It may grow much larger over the years and removal is sometimes recommended not just for cosmetic reason, especially if they get irritated and bleed easily. It is easily removed by scrapping off with the based cauterized afterwards, or the whole thing can be burn off by a CO2 laser, or freezed off using liquid nitrogen. Occasionally it may turn black and become difficult to distinguish from a skin cancer, in which case removing it intact for examination is mandatory.