Topical Fluorouracil: What It Treats and How to Use It

Topical fluorouracil (often called 5-FU) is a prescription cream used to treat sun-damaged skin, actinic keratoses, and some superficial skin cancers. It works by targeting abnormal skin cells so they clear away over weeks. You’ll often see the treated area get red, crust, and peel — that’s normal and usually means the medicine is working.

How to apply topical fluorouracil

Follow your prescriber’s instructions. Commonly, you wash and dry the area, then apply a thin layer once or twice daily for the time your doctor prescribes. Don’t rub it in aggressively. Avoid eyes, mouth, and open wounds. Use only on the exact area advised — treating more skin won’t speed things up and can increase irritation.

Expect the treated spots to worsen before they improve. Over 2–6 weeks you may see increasing redness, burning, swelling, scabs, and peeling. After stopping treatment, healing can continue for several weeks to months. Protect that area from sunlight while healing: use sunscreen, wear hats, and avoid tanning.

Side effects, risks and safe buying tips

Common local side effects include redness, burning, itching, soreness, and flaking. Most are temporary. Contact your doctor if you get severe pain, large blisters, spreading rash, fever, or signs of infection. Systemic side effects are rare with topical use, but tell your doctor if you’re pregnant, breastfeeding, or have open wounds over large areas.

Topical fluorouracil is a prescription drug in many countries. If you’re thinking of buying it online, do this: use pharmacies that require a prescription, check for clear contact info and licensing, read recent reviews, and avoid extremely low prices that look suspicious. Keep records of batch numbers and expiry dates when you receive medicine. If a site offers to prescribe without a proper medical consult, walk away and talk to your healthcare provider instead.

Simple application tips: apply at the same time each day, wash hands after applying unless your hands are the treated area, and don’t cover the area with airtight dressings unless your doctor says to. If you plan cosmetic procedures or laser treatment later, tell your provider you used 5-FU recently — treated skin can be more sensitive for months.

Your doctor may suggest follow-up checks to see how well treatment worked. Sometimes one course is enough. Other times a repeat or different therapy (cryotherapy, photodynamic therapy, or surgical removal) may be needed. If you’re unsure about the diagnosis or treatment plan, ask for clear reasons and expected timelines from your provider.

Bottom line: topical fluorouracil is effective for many sun-related skin problems, but it causes visible skin reactions while working. Use it exactly as prescribed, protect the area from sun, watch for severe reactions, and only buy from trustworthy pharmacies that require a prescription.