In dermatology, AK stands for actinic keratosis, a rough, scaly patch of skin caused by years of sun exposure. These spots are considered precancerous because roughly 10% of them will eventually develop into squamous cell carcinoma, a common type of skin cancer. With a global prevalence of about 14% in the general population, AKs are one of the most frequently treated conditions in dermatology offices.
How AKs Develop
Actinic keratoses form when cumulative UV radiation damages the skin cells in your outermost layer of skin (the epidermis). Over time, this damage disrupts the normal controls on cell growth and differentiation. The affected cells begin to multiply abnormally, creating a visible patch of thickened, disordered skin. This isn’t a one-time sunburn problem. AKs result from decades of sun exposure adding up, which is why they’re sometimes called solar keratoses and are far more common in people over 50.
The UV damage also suppresses local immune responses in the skin, making it harder for your body to clear out these abnormal cells on its own. That combination of unchecked cell growth and reduced immune surveillance is what makes AKs a stepping stone toward skin cancer rather than just a cosmetic issue.
What AKs Look and Feel Like
Most AKs are small, typically less than an inch (2.5 cm) across. They can be flat or slightly raised and range in color from pink to red to brown, sometimes blending with surrounding skin so closely that you feel them before you see them. The hallmark is a rough, sandpaper-like texture that catches your finger when you run it across the spot.
Some AKs develop a hard, wartlike surface. Others stay subtle, presenting as a patch of dry, flaky skin that never quite heals. Itching, burning, and occasional bleeding or crusting are common. They show up almost exclusively on sun-exposed areas: the face, ears, lips, scalp (especially in people with thinning hair), neck, forearms, and the backs of the hands. If you have one, you likely have others, since the same sun damage that created one spot has affected the surrounding skin too.
When AKs Become Dangerous
About 10% of actinic keratoses progress to squamous cell carcinoma, and that progression typically takes around two years. The challenge is that there’s no reliable way to predict which individual spots will turn cancerous and which will stay put or even fade on their own. That unpredictability is the main reason dermatologists recommend treating AKs rather than watching and waiting.
Signs that an AK may be progressing include rapid growth, increasing thickness, tenderness, or a spot that bleeds easily. A biopsy is typically performed when a lesion looks suspicious, keeps coming back after treatment, or doesn’t respond to standard therapy.
Treatment Options
Most AKs are treated in a dermatologist’s office or with prescription creams at home. The right approach depends on how many spots you have, how thick they are, and where they’re located.
Freezing (Cryotherapy)
The most common in-office treatment involves applying liquid nitrogen directly to the spot. The freeze destroys the abnormal cells, and the area heals over the following weeks. A standard protocol uses one or two freeze-thaw cycles lasting 5 to 20 seconds each. Cure rates vary significantly based on how long the freeze is held, ranging from about 39% with a brief 5-second application up to 83% with longer freezing times. Thicker, crustier spots sometimes need gentle scraping beforehand (curettage) or a topical softening agent applied for a couple of weeks before freezing.
Prescription Creams
When you have many AKs spread across a larger area, topical treatments can address the entire field of sun-damaged skin rather than one spot at a time. One widely used option is an immune-stimulating cream applied three times per week for 16 weeks. It works by triggering your immune system to attack the abnormal cells. The tradeoff is significant skin irritation during treatment: redness, swelling, crusting, scaling, and sometimes ulceration in the treated area. These reactions are expected and generally a sign the treatment is working, but they can be uncomfortable enough that some people struggle to complete the full course.
Another common topical option is a chemotherapy cream that kills rapidly dividing cells. It’s applied daily for several weeks and produces similar inflammatory reactions. Both creams have the advantage of treating sun damage you can’t yet see, potentially clearing precancerous changes before they become visible AKs.
Photodynamic Therapy
This two-step procedure involves applying a light-sensitive solution to the skin, then activating it with a specific wavelength of light. The solution is absorbed preferentially by abnormal cells, so when the light triggers a chemical reaction, it selectively destroys the AK tissue while sparing healthy skin. Blue light is typically used for superficial lesions like AKs, while red light penetrates deeper for thicker growths.
The incubation time for the solution varies. One formulation requires about three hours under a bandage, while another needs 14 to 18 hours for full absorption. After the light treatment, the skin becomes red, swollen, and sensitive for several days to a couple of weeks. You’ll need to avoid sun exposure during this healing period. Photodynamic therapy is particularly useful for treating broad areas of the face or scalp where multiple AKs have developed.
Preventing New AKs
Since AKs are driven by cumulative UV damage, consistent sun protection is the single most effective way to prevent new spots and reduce recurrence after treatment. High-SPF broad-spectrum sunscreen (SPF 50 or higher), applied daily to exposed skin, slows the development of new lesions. Some newer sunscreen formulations that include DNA repair enzymes have shown the ability to improve existing AKs and the surrounding field of damaged skin, not just block further UV exposure.
Beyond sunscreen, protective clothing, wide-brimmed hats, and avoiding peak sun hours all reduce UV accumulation. If you’ve been treated for AKs, regular skin checks with a dermatologist (typically every 6 to 12 months) help catch new or recurring spots early, when they’re easiest to treat and long before any risk of progression to skin cancer.