Actinic keratosis

Also known as: solar keratosis; AK

UV-induced dysplastic keratinocyte lesions — a marker of field change and, in a small proportion, a precursor of invasive cSCC. Management ranges from emollients and field therapy to cryotherapy, excision and prevention strategies.

CurrentLast reviewed 15 March 2026

Classification

The Olsen clinical grading:

Grade 1: flat pink macule, slightly palpable ('feel, rather than see').
Grade 2: moderately thick; both visible and palpable hyperkeratosis.
Grade 3: very thick or hyperkeratotic; consider biopsy to exclude cSCC.

Management

Lesion-directed

Cryotherapy — first-line for isolated hyperkeratotic AK.
Curettage & cautery — hyperkeratotic or recalcitrant; provides histology.
Excision — any AK suspicious for invasive cSCC.

Field therapy

Topical 5-FU 5% — 2–4 weeks bd; brisk inflammation; highest clearance.
Imiquimod — immune-mediated; 5%: 3×/week for 4 weeks; 3.75%: once daily as two 2-week cycles over 6 weeks.
Diclofenac 3% gel — 60–90 days; well-tolerated, lower efficacy.
MAL-PDT — 1–2 sessions; high clearance for thin AK.
Tirbanibulin ointment — 5 days daily.

Prevention

Broad-spectrum SPF 30+ daily to exposed sites; sun-protective clothing.
Annual skin review for multiple AKs or field change.
Nicotinamide 500 mg bd (ONTRAC) — reduces AK and cSCC incidence in high-risk patients.

UK practiceWhen to refer

Refer to secondary-care dermatology or 2WW if: rapid growth, induration, tenderness, ulceration, bleeding, immunosuppression with multiple AKs, or failure of two appropriate field therapies.

References

de Berker D, McGregor JM, Hughes BR. British Association of Dermatologists' guidelines for the care of patients with actinic keratosis 2017. Br J Dermatol. 2017;176(1):20-43.

Chen AC et al. A phase 3 randomized trial of nicotinamide for skin-cancer chemoprevention (ONTRAC). N Engl J Med; 2015.