Actinic keratoses are rough, scaly patches caused by years of sun exposure. They often develop on the face, scalp, chest, arms, or hands and are considered precancerous. If untreated, some AKs can turn into squamous cell carcinoma.
5-Fluorouracil (5-FU) is a topical chemotherapy cream used to eliminate abnormal sun-damaged skin cells. It’s especially effective for treating multiple AKs or areas with widespread sun damage—called field therapy.
• Cleanse: Wash skin with a gentle cleanser and pat dry.
• Apply: Use a thin layer of prescribed cream or lotion on affected areas at bedtime.
• Wash hands: Immediately after each use or use gloves to put it on.
• Avoid: Eyes, nostrils, lips, and open wounds. Do not let your pets lick your treated skin as this medicine can be deadly for them.
Most patients apply 5-FU for 2 to 4 weeks, depending on treatment area, extent of sun damage, and individual’s response to treatment.
Mild redness and irritation are expected during the first week. During the second week the reaction intensifies with increased redness, flaking, crusting, stinging or burning. Typically, we ask patients to stop treatment at this stage, so it does not progress to oozing or scabbing. This is normal—this means the treatment is working.
It’s very important to protect your skin during and after treatment from sun exposure. Regular sunscreen and sun protective clothing is highly recommended.
Healing typically begins once the cream is stopped. Healthy new skin appears within 1 to 4 weeks. Treated areas often look smoother and less sun-damaged
Do not use 5-FU if you are:
• Pregnant or breastfeeding
• Allergic to fluorouracil
• Using other irritating topical treatments (unless cleared by your provider)
Use with caution if:
• You have a weakened immune system
• You’re taking medications that slow healing
• Moisturize: Use a gentle, fragrance-free cream to reduce dryness (ask us for suggestions)
• Sun Protection: Stay indoors or wear mineral sunscreen + wide-brim hats
• Cool Compresses: Help ease stinging and inflammation
• Do NOT pick: Allow skin to shed naturally to avoid infection and scarring
• Pain Relief: Use OTC meds like acetaminophen or ibuprofen if needed
Is the reaction supposed to look this bad?
Yes—redness, peeling, crusting, and oozing are expected. It means the treatment is targeting abnormal cells.
Can I stop early if it looks better?
No—finishing the full course ensures all precancerous cells are treated. Always check with your provider before stopping.
How do I know it worked?
As treated skin heals, it often looks clearer, smoother, and less sun damaged. We’ll assess your results at your follow-up visit.
Your Skin, Renewed
While 5-FU treatment can be intense, it is highly effective. With guidance, support, and patience, most patients achieve excellent results with long-lasting skin health benefits.
Need Help?
Book an appointment with one of our board-certified dermatologists.
Disclaimer: The photos shown are actual images of our patient, shared with explicit written consent. These images are for educational use only and may not be copied, distributed, or reproduced without permission from our office.