Keratosis isn’t a single condition. It’s a family of skin growths that share one thing in common: an excess buildup of keratin, the protein that forms your outer layer of skin. What keratosis looks like depends entirely on which type you have, and the differences are dramatic. Some appear as rough, sandpaper-like patches. Others look like waxy, brown growths that seem glued onto the skin. Here’s how to tell them apart.
Actinic Keratosis: Rough, Scaly Patches
Actinic keratosis is the type most people worry about, because it’s caused by sun damage and carries a small risk of becoming skin cancer. These lesions show up on sun-exposed areas: the face, scalp (especially in people with thinning hair), ears, forearms, and backs of the hands.
In its earliest stage, actinic keratosis is easier to feel than to see. It starts as a small, slightly reddish patch with a gritty, sandpaper-like texture you notice when you run your fingers across your skin. The color is typically pink to red, and the surface is covered in dry, white or yellowish scales. As the lesion progresses, the scaling becomes thicker and more obvious, forming a raised, crusty plaque that’s hard to miss. Some actinic keratoses develop a brownish pigmentation rather than the classic redness, particularly on darker skin tones.
The risk of any single actinic keratosis turning into squamous cell carcinoma is low, estimated between 0 and 0.075% per lesion per year. But that risk climbs when you have multiple lesions across a broad area of sun-damaged skin. Signs that a lesion may be changing include rapid growth, increasing thickness, tenderness, or bleeding.
Seborrheic Keratosis: Waxy, “Stuck-On” Growths
Seborrheic keratosis is the most common benign skin growth in older adults, and it has a very distinctive look. These lesions appear as raised, waxy, scaly bumps that look like they’ve been pasted onto the skin’s surface. Dermatologists often describe them as having a “stuck-on” appearance, and once you see one, that description makes immediate sense. They look like they could be peeled right off (though you shouldn’t try).
The color range is wide. A single seborrheic keratosis can be light tan, dark brown, yellowish, grey, or nearly black. The surface has a dull, slightly greasy or waxy texture, often with visible tiny pits or a crumbly, wart-like quality. They can appear as a single spot or in clusters of dozens, even hundreds, mostly on the chest, back, face, and shoulders. They tend to multiply with age.
In people with darker skin, a specific variant called dermatosis papulosa nigra is common. These show up as small brown-to-black papules concentrated on the face and neck, increasing in number over the years.
Because darkly pigmented seborrheic keratoses can resemble melanoma, they sometimes cause alarm. The key visual difference is that seborrheic keratoses have a uniform, stuck-on quality with a clearly defined border sitting above the skin’s surface. Melanomas, by contrast, tend to show irregular color patterns, uneven borders, and a blue-black tone that blends into the surrounding skin rather than sitting on top of it.
Keratosis Pilaris: Tiny Bumps Like Chicken Skin
Keratosis pilaris looks completely different from the other types. It appears as clusters of very small, painless bumps that give your skin the texture of sandpaper or permanent goosebumps. People often call it “chicken skin.” The bumps are caused by tiny plugs of keratin that block individual hair follicles.
You’ll find keratosis pilaris most often on the upper arms, outer thighs, cheeks, and buttocks. The bumps themselves are usually skin-colored or slightly pink, and the surrounding skin feels dry and rough. They don’t hurt or itch in most cases, though the skin can feel tight or irritated in dry weather. The condition is extremely common, especially in children and teenagers, and often improves with age.
A facial variant produces follicular bumps surrounded by a ring of redness on the cheeks, forehead, and chin. In some cases, this form can also cause gradual thinning of the outer portion of the eyebrows over time.
Stucco Keratosis: White Spots on the Legs
Stucco keratosis is a lesser-known type that appears almost exclusively on the lower legs and ankles, though it occasionally shows up on the forearms. The lesions are small, typically under 1 centimeter, and white or grey in color. They have a dry, rough surface and look a bit like small patches of dried plaster or stucco stuck to the skin, which is where the name comes from.
These are most common in older adults and are completely benign. They’re sometimes mistaken for warts, but their flat, scaly texture and consistent white color set them apart.
How to Tell the Types Apart
- Location matters most. Rough patches on sun-exposed skin point to actinic keratosis. Tiny bumps on the upper arms and thighs suggest keratosis pilaris. Waxy brown growths on the trunk are likely seborrheic keratosis. White, scaly spots on the lower legs indicate stucco keratosis.
- Texture is a strong clue. Actinic keratosis feels gritty and sandpaper-like on flat skin. Keratosis pilaris feels like a field of tiny raised dots. Seborrheic keratosis feels waxy and slightly greasy.
- Color narrows it down. Pink or red with white scaling suggests actinic. Tan to dark brown with a waxy sheen suggests seborrheic. Skin-colored tiny bumps suggest keratosis pilaris. White and chalky suggests stucco keratosis.
When Appearance Alone Isn’t Enough
Most keratoses are identifiable by sight, but there are situations where visual assessment gets tricky. A darkly pigmented seborrheic keratosis can look alarmingly like melanoma. An actinic keratosis that becomes thicker, starts bleeding, or develops a raised, firm base may be transitioning toward squamous cell carcinoma. And flat, corn-like bumps on the palms or soles, a rare type called arsenical keratosis linked to chronic arsenic exposure, can mimic calluses or warts.
Any skin growth that changes rapidly in size, shape, or color, or that bleeds without being scratched or bumped, warrants a closer look. A dermatologist can examine questionable spots with a dermatoscope, a magnifying tool that reveals internal structures invisible to the naked eye, such as tiny cysts and blood vessel patterns that reliably distinguish benign growths from potentially dangerous ones.