In dermatology, AK stands for actinic keratosis, a rough, scaly patch of skin caused by years of ultraviolet (UV) light exposure. These patches are considered precancerous because they can, in some cases, develop into squamous cell carcinoma, a common form of skin cancer. AKs are among the most frequent reasons people visit a dermatologist, and they’re highly treatable when caught early.
What Actinic Keratosis Looks and Feels Like
An actinic keratosis typically appears as a rough, dry, or scaly patch smaller than one inch across. Many people notice them by touch before they see them. Early lesions are only slightly raised and better felt than seen. More developed ones become clearly visible, moderately thick patches. Advanced AKs can grow very thick with a hard, wartlike surface.
Color varies. Some are pink or red, others brown, and some blend closely with surrounding skin. They can itch, burn, bleed, or form a crust. You’ll almost always find them on sun-exposed areas: the face, ears, lips, scalp (especially in people with thinning hair), the back of the hands, the neck, and the forearms. It’s common to have more than one at a time.
How UV Damage Creates These Lesions
Actinic keratoses form when UV radiation damages the DNA inside skin cells called keratinocytes. Both types of UV light contribute, but in different ways. UVA light, which penetrates deeper into the skin, generates reactive oxygen species that disrupt normal cell signaling and trigger abnormal cell growth. UVB light directly damages DNA strands, creating the kind of mutations most closely linked to skin cancer development.
One of the most critical changes involves a tumor suppressor gene called p53, which normally helps repair damaged DNA or tells defective cells to self-destruct. UVB light can knock this gene out of action. Mutations in p53 have been found in over 90% of squamous cell carcinomas. When p53 stops working, other DNA errors accumulate unchecked, pushing cells further down the path toward cancer. UV exposure also triggers inflammation in the skin, compounding the damage over time.
Who Is Most at Risk
The single biggest risk factor is cumulative UV exposure over a lifetime. The more days per week you spend in the sun and the more years that exposure adds up, the greater your risk and the more lesions you’re likely to develop.
Skin type matters significantly. People with very fair skin (Fitzpatrick skin types 1 and 2) carry the highest risk. In one study, 100% of men with the fairest skin type who had AK presented with five or more lesions, compared to about 52% of men with a medium skin tone. None of the men with darker skin types (4 and 5) had that many. The pattern held for women too, though the gap was somewhat narrower. Age and sex are also independent risk factors, with AKs becoming increasingly common after age 50.
Can an AK Become Skin Cancer?
Yes, but the risk for any single lesion is relatively low. Published estimates for an individual actinic keratosis progressing to invasive squamous cell carcinoma range from about 0.025% to 16% per year. That’s a wide range because progression depends on many factors, including the thickness of the lesion, how many you have, and your immune health.
The trouble is that dermatologists can’t reliably predict which specific spots will progress and which won’t. People with multiple AKs face a cumulative risk that adds up over time. This is why treatment is generally recommended rather than a wait-and-see approach, particularly for thicker or symptomatic lesions.
Field Cancerization: Why the Whole Area Matters
An important concept in AK management is field cancerization. The skin surrounding a visible actinic keratosis has often sustained the same UV damage, even if it looks normal. These areas harbor precancerous changes at the cellular level and carry an increased risk of developing new AKs or progressing to squamous cell carcinoma. This is why dermatologists sometimes treat an entire region of skin rather than just individual spots. Field-directed treatments reduce recurrence rates and may lower the overall risk of skin cancer in that area.
Treatment Options
Treatment falls into two broad categories: spot treatments for individual lesions and field therapies for larger areas of damaged skin. The American Academy of Dermatology gives its strongest recommendations to cryosurgery, two topical creams (imiquimod and fluorouracil), and UV protection. A newer topical ointment, tirbanibulin, also received a strong recommendation in 2022. Photodynamic therapy and a topical anti-inflammatory gel (diclofenac) are conditionally recommended.
Cryosurgery
Cryosurgery, or “freezing,” is the most common in-office treatment for individual AKs. Your dermatologist applies liquid nitrogen directly to the lesion for a few seconds. Complete clearance rates in studies run around 52%, though many lesions need more than one session. The treated spot typically blisters, crusts over, and heals within a few weeks. Pain during the procedure is moderate, averaging about 3.2 on a 10-point scale in clinical trials, with noticeable swelling and redness afterward.
Topical Creams and Ointments
For people with multiple AKs or widespread sun damage, topical treatments can cover a larger field. These are applied at home over a set course, and the treated skin goes through a predictable inflammatory reaction before healing.
- Fluorouracil (5-FU) cream: Applied twice daily for two to four weeks. This is one of the most widely used options. It causes redness, burning, dryness, and sometimes erosion or crusting in the treated area. The reaction looks dramatic but is expected and temporary.
- Imiquimod cream: Applied once daily in two two-week cycles with a two-week rest period in between. Side effects include redness, crusting, scabbing, and sometimes fatigue or body aches.
- Tirbanibulin ointment: The shortest course available, applied once daily for just five consecutive days. Local skin reactions like redness, scaling, and crusting are typically mild to moderate.
- Diclofenac gel: Applied twice daily for 60 to 90 days. The longest treatment course but generally the mildest in terms of skin reactions, making it an option for people who can’t tolerate more aggressive therapies.
With all topical treatments, the skin will look worse before it looks better. Redness, peeling, and crusting are signs the treatment is working. Most people’s skin returns to normal within a few weeks of finishing the course.
Photodynamic Therapy
Photodynamic therapy (PDT) involves applying a light-sensitizing solution to the skin and then exposing it to a specific wavelength of light. The solution is absorbed preferentially by abnormal cells, which are then destroyed when activated by the light. Daylight PDT, a version done with natural sunlight rather than a lamp, clears about 64% of lesions and causes significantly less pain than cryosurgery (averaging 0.9 versus 3.2 on a 10-point pain scale). Swelling and redness are also milder. PDT is particularly useful for treating large areas of the face or scalp.
How Sunscreen Reduces Your Risk
Regular sunscreen use is one of the clearest, most evidence-backed ways to prevent new actinic keratoses and even help existing ones fade. A landmark study published in the New England Journal of Medicine found that people who used sunscreen regularly developed 38% fewer new AKs than those who used a base cream without UV protection. The sunscreen group also had significantly more remissions of existing lesions. The benefit followed a dose-response pattern: the more sunscreen people applied, the fewer new spots appeared and the more existing ones resolved.
Broad-spectrum sunscreen with SPF 30 or higher, reapplied every two hours during sun exposure, is the standard recommendation. Protective clothing, wide-brimmed hats, and seeking shade during peak UV hours all complement sunscreen use. For people who already have AKs, these habits help slow the development of new lesions and support the results of any treatment they’ve received.