What Side Effects Should You Expect From Carac?

Carac (Fluorouracil 0.5% cream) is a topical medication used to treat actinic keratoses — precancerous skin patches caused by sun damage. It works by destroying abnormal skin cells, which means some skin irritation during treatment is not just normal — it's actually a sign the medication is working.

That said, it's important to understand the difference between expected side effects and warning signs that need medical attention. This guide breaks it all down.

Common Side Effects of Carac

Most people who use Carac experience some degree of local skin reactions. These are the most common side effects:

• Redness (erythema) — The treated area will likely become red within the first week. This is the most common reaction.
• Burning and stinging — A burning or stinging sensation when you apply the cream is normal, especially in the first few days.
• Pain and tenderness — The skin may feel sore to the touch as the medication works on the damaged cells.
• Crusting and scaling — As abnormal cells are destroyed, the skin may crust over and peel. This is part of the healing process.
• Dryness — The treated area may become dry and flaky.
• Swelling — Mild swelling around the application site is common.
• Erosion — In some cases, the skin may develop shallow, open areas as damaged cells are shed.
• Hyperpigmentation — The treated skin may temporarily darken. This usually fades after treatment ends.

These reactions typically peak around weeks 2-3 of treatment and then gradually improve after you stop applying Carac. The full healing process can take several weeks after your treatment course is complete.

Why the Side Effects Are Actually a Good Sign

This might sound counterintuitive, but the redness, crusting, and irritation you see during Carac treatment mean the medication is reaching the damaged cells. Areas with more sun damage often react more strongly. If you see very little reaction, it could mean the medication isn't reaching all of the affected areas — let your doctor know.

Serious Side Effects: When to Call Your Doctor

While local skin irritation is expected, some reactions require medical attention. Call your doctor right away if you experience:

• Severe allergic reaction — Signs include hives, difficulty breathing, swelling of the face, lips, tongue, or throat. Seek emergency help immediately.
• Extreme pain or burning — Some discomfort is normal, but if the pain is severe enough to interfere with sleep or daily activities, contact your doctor.
• Signs of infection — Increasing redness that spreads beyond the treatment area, pus, warmth, fever, or worsening pain could indicate an infection in the treated skin.
• Eye irritation — If Carac gets near your eyes and causes burning, redness, or vision changes, flush with water and contact your doctor.
• Unusual bleeding — Mild oozing is normal, but significant or persistent bleeding is not.

Side Effects in Specific Populations

Pregnancy and Breastfeeding

Carac is Pregnancy Category X, meaning it should never be used during pregnancy. Fluorouracil can cause miscarriage or birth defects. If you are pregnant or think you might be pregnant, do not use Carac. It is also not recommended while breastfeeding.

If you become pregnant during treatment, stop using Carac immediately and contact your doctor.

Older Adults

Carac is commonly used in older adults since actinic keratoses are most common in people with decades of sun exposure. No dose adjustment is needed, but older skin may be more sensitive. Your doctor might suggest a shorter treatment period or more frequent check-ins.

Children

Safety and effectiveness of Carac have not been established in children. It is not typically prescribed for pediatric patients.

How to Manage Carac Side Effects

You don't have to just tough it out. Here are practical tips for managing discomfort during treatment:

Skin Care During Treatment

• Use a gentle moisturizer — Apply a plain, fragrance-free moisturizer to the surrounding (untreated) skin. Ask your doctor if you can apply moisturizer to the treated area between applications.
• Avoid harsh products — Skip exfoliants, retinoids, glycolic acid, and other irritating products on or near the treated area.
• Protect from the sun — Fluorouracil makes your skin more sensitive to UV light. Wear a broad-spectrum sunscreen (SPF 30+) on treated areas and avoid prolonged sun exposure.
• Don't cover with tight bandages — Unless your doctor tells you otherwise, avoid occlusive dressings over the treated area.

Pain Management

• Cool compresses — A cool, damp cloth can soothe burning and stinging.
• Over-the-counter pain relief — Acetaminophen or ibuprofen can help with pain and discomfort. Ask your doctor or pharmacist first.
• Talk to your doctor about breaks — If side effects become unbearable, your doctor may adjust your treatment schedule rather than having you stop completely.

What NOT to Do

• Don't stop treatment early without talking to your doctor. The treatment needs to run its full course to be effective.
• Don't apply more than directed — Using extra cream won't speed up results but will increase side effects.
• Don't pick at crusts or peeling skin — Let the skin heal naturally to reduce scarring risk.

What Happens After Treatment Ends?

Once you complete your Carac treatment course (typically up to 4 weeks), the skin will continue to heal for another 2 to 8 weeks. During this time:

• Redness and irritation will gradually fade
• Crusting will resolve as new, healthy skin grows in
• Any hyperpigmentation usually fades over several weeks to months
• The treated area may initially look worse before it looks better — this is normal

Your doctor will likely schedule a follow-up visit 2 to 4 weeks after treatment to evaluate the results.

Final Thoughts

Carac side effects can look and feel alarming, but most of them are a normal part of the treatment working. The key is knowing the difference between expected irritation and something that needs medical attention.

If you're experiencing side effects that worry you, call your doctor — they can help you manage symptoms and adjust your treatment plan if needed. And if you're just starting Carac and want to understand the medication better, check out our guides on what Carac is and how it's used and how Carac works.

Having trouble finding Carac at your pharmacy? Use Medfinder to check which pharmacies have it in stock.