Seborrheic keratosis: the "stuck-on" spots
Many people notice raised, waxy, brown or tan spots that look like they've been stuck onto the skin. These are usually seborrheic keratoses (SKs), one of the most common skin growths in adults. They aren't caused by the sun in the way sun spots are, and they don't turn into cancer, but they can look enough like skin cancer that a doctor should check any new or unusual one.
- Seborrheic keratoses are harmless warty spots; over 90% of adults over 60 have at least one.
- They aren't premalignant, but some skin cancers look similar, so get new, changing or unusual spots checked.
- They can be removed if they itch, catch on clothing or bother you; there's no known way to prevent them.
What they are
According to DermNet: Seborrhoeic keratosis, a seborrheic keratosis is "a harmless warty spot that appears during adult life as a common sign of skin ageing." Other names include basal cell papilloma, senile wart, brown wart and barnacle. Despite the name, they aren't related to oil glands or sebum.
Who gets them
DermNet estimates that over 90% of adults over 60 have one or more. They occur in all races and both sexes, usually starting in the 30s or 40s, and are uncommon under 20. Some people inherit a tendency to get many. Some arise from a solar lentigo (see sun spots), and the gene changes involved suggest UV plays a role in those on the head and neck.
What they look like
- Flat or raised, from 1 mm to several centimeters.
- Skin-colored, yellow, gray, light or dark brown, black or mixed.
- Smooth, waxy or warty surface; they look stuck on.
- Anywhere except the palms and soles, often in groups on the scalp, back, under the breasts or in the groin.
Why a doctor should look
DermNet is clear that SKs "are not premalignant tumours." However, skin cancers such as basal cell carcinoma, squamous cell carcinoma or melanoma can be hard to tell apart from them, and a cancer can occasionally arise next to one. Doctors use dermoscopy to look for typical SK features and may biopsy if in doubt. Very rarely, a sudden eruption of many SKs can signal an internal cancer, which is another reason to mention a sudden crop to your doctor.
See a dermatologist if a spot is new after middle age, grows quickly, bleeds, looks different from your other spots, or has the warning signs in the ABCDE check. Don't try to cut or burn one off at home.
Removal
An SK can be removed if it's unsightly, itchy or catches on clothing. DermNet lists cryotherapy (liquid nitrogen), curettage and/or electrocautery, ablative laser, shave removal and focal chemical peel. All have downsides; loss of pigmentation is a particular issue for darker skin. There's no known way to prevent them, but sun protection still matters for preventing the spots that are dangerous (see daily habits to lower skin cancer risk).
Educational information only, not medical advice. See a board-certified dermatologist for diagnosis and treatment. See our medical disclaimer.
Published October 29, 2026. Sources are linked in the text. See our Medical Disclaimer.