How long does topical 5-fluorouracil take to work for actinic keratosis?

Actinic keratosis is a sun-related rough or scaly skin change. 5-fluorouracil acts on abnormal surface cells, so visible inflammation can develop before the area settles. The reaction may be more noticeable where several damaged spots are close together, and not every treated patch behaves identically. Timing depends on the prescribed regimen, the body site, and your skin's sensitivity. A temporary flare does not by itself show whether every lesion has cleared; that is why follow-up matters.

Follow the prescription exactly and apply the medicine only to the planned area. Wash your hands after use, avoid picking crusts, and protect the treated skin from sunlight. Do not add steroid creams, dressings, cosmetics, or other active products unless your clinician has approved them. If irritation becomes difficult to manage, contact the prescriber for specific instructions instead of shortening or extending the course yourself.

Contact your clinician promptly for severe pain, rapidly increasing swelling, spreading redness, pus, fever, or a reaction involving the eyes. Seek urgent help for facial swelling with breathing difficulty. Have any spot that remains thick, tender, bleeding, ulcerated, or non-healing examined after treatment; persistent change may need assessment rather than being labelled a normal medicine reaction.

Ask when your prescribed course finishes, which reaction is expected at your treatment site, and what cleanser or moisturiser is suitable. Confirm when the skin should be reviewed, how missed applications are handled, and how a lesion that remains rough or thick will be reassessed.