What does topical 5-fluorouracil treat?

This prescription cream targets rapidly dividing abnormal cells in the treated area. It is commonly used for actinic keratosis, rough sun-damaged patches that can sometimes progress to skin cancer, and actinic cheilitis affecting the lip. A clinician may also prescribe it for selected superficial Bowen's disease, an early form of squamous cell carcinoma in the outer skin layers. The treatment is not suitable for every lesion, and a thick, painful, bleeding, or raised area may need examination or a procedure rather than cream alone.

Use the cream only on the areas and for the schedule prescribed. Redness, scaling, soreness, crusting, and irritation can develop as abnormal cells respond; do not increase the amount or frequency to speed the process. Protect treated skin from direct sun and avoid applying the cream near the eyes, inside the mouth, or on broken skin unless specifically instructed. Wash hands after application and keep follow-up appointments so the clinician can check healing and decide whether any lesion needs further assessment.

Contact the prescriber if pain, swelling, ulceration, or irritation becomes difficult to manage, or if the reaction extends well beyond the treatment area. Seek urgent help for facial swelling, breathing difficulty, widespread blistering, or a severe allergic-looking reaction. Arrange review for a lesion that bleeds, grows, becomes thick or tender, or fails to settle as expected.

Which lesion are we treating, and why is this cream appropriate? What schedule and amount should I use? Which reactions are expected, and when should I pause and call? How will you confirm that a persistent or thickened spot needs another treatment?