Efudix (Efudex) Healing Stages: A Week-by-Week Timeline

The most common questions we hear about Efudix (5-fluorouracil) are not about whether to use it — they are about the ride: what will my skin look like in week two? How long until I look normal? Is this reaction too much?

This guide walks the whole arc, stage by stage — with photographs showing what a full-face field treatment looks like as the reaction develops. It is a companion to our full Efudix patient guide, which covers how the cream works, how to apply it and its side effects in detail. Timings below are typical patterns, not promises — the site treated, the course your doctor prescribed and the amount of underlying sun damage all shift the curve.

Why the reaction happens at all

Efudix is a topical chemotherapy: it blocks an enzyme that dividing cells need to make DNA, so it preferentially damages the rapidly dividing abnormal cells in actinic keratosis and SCC in situ. ⁽¹⁾ The visible inflammation is the skin clearing those damaged cells — which is why the areas with the most sun damage often light up the most, including spots you could not see before treatment.

Days 1–5 — the quiet start

What is normal: not much. Mild redness, dryness and a little stinging at the treated site. Many patients wonder whether the cream is doing anything.

What helps: settle into the routine — consistent application as prescribed, hands washed after every dose, and moisturiser, sunscreen or make-up once the cream has absorbed (often around 20 minutes).

Call if: you develop immediate severe burning, swelling or blistering out of proportion to a mild sting — uncommon this early and worth checking.

Days 5–14 — the build

What is normal: the reaction announces itself. Increasing redness, burning and tenderness, some swelling. Sun-damaged patches begin to “light up” — often unevenly, so the area can look blotchy. Discomfort builds steadily.

What helps: keep going unless advised otherwise — this build is expected. Bland moisturiser for comfort, loose clothing over treated body sites, and start planning around the peak if you are treating your face (many patients arrange 2–4 weeks of reduced social or work commitments).

Call if: the reaction is spreading well beyond the area you were asked to treat, or you are already struggling to continue — plans can often be adjusted early rather than abandoned late.

Weeks 2–6 — the peak

What is normal: this is the stage that shocks people who were not warned. Peak inflammation — deep redness, cracking, crusting and sometimes weeping. Facial movement (talking, eating, laughing) can be uncomfortable. Many patients describe it as the worst sunburn of their life, except it keeps building instead of fading. However dramatic it looks, this is the medicine doing its job — and published analyses have found that a stronger local reaction is associated with better clearance of actinic keratosis. ^(3,4)

What helps: bland moisturiser as often as needed, gentle warm-water washing, and resisting the urge to pick crusts. Severity is not a target — you do not need to chase a worse reaction for a better result.

Call if: you genuinely cannot tolerate the pain despite simple measures; you see possible infection signs (spreading redness, increasing pain, pus, fever) — noting a normal peak can mimic infection, so when in doubt, get it checked; or you develop any whole-body symptoms (severe abdominal pain, vomiting, bloody diarrhoea, mouth or tongue soreness, fevers and chills) — these are rare but need urgent review.

One rule matters more than any other at this stage: stop on the date your doctor set — not when the reaction looks its worst, and not because the skin briefly looks better. Stopping early can leave abnormal cells under-treated; if you are struggling, contact the clinic to adjust the plan rather than quietly stopping. Course length is individual — commonly around 4 weeks for actinic keratosis and about 6 weeks for SCC in situ — and it is set by your doctor, not by the calendar on this page.

The day you stop — what the end looks like

By the planned stop date the treated area is typically red, crusted and tender — sometimes cracked or weeping. That is the expected end-state, not a sign something has gone wrong. The key reassurance: it does not keep getting worse once you stop. From the last application, the skin begins to settle.

Weeks 1–2 after stopping — settling

What is normal: the angry redness starts to calm, weeping dries, crusts begin lifting on their own, and comfort improves noticeably week on week. The area still looks obviously “treated”.

What helps: this is where aftercare earns its keep —

• moisturise frequently with a plain, bland emollient — the single most helpful thing for comfort and recovery;
• strict sun avoidance, adding daily SPF 50+ as soon as the skin tolerates it — freshly treated skin is very UV-sensitive;
• no picking or scrubbing — let crusts lift on their own;
• keep active skincare paused (acids, retinoids, scrubs) until fully settled.

Call if: pain is increasing rather than decreasing after stopping, or anything looks infected.

Weeks 2–4 after stopping — presentable again

What is normal: crusting resolves and new skin covers the area — often pink, smooth and a little shiny at first. Most patients treating their face feel comfortable in public somewhere in this window, which is why many plan 2–4 weeks of downtime from the peak onward. Make-up is usually fine again once the surface has healed over.

What helps: keep the moisturiser and daily SPF habit — it protects the result as well as the recovery.

Call if: any raw area is not steadily improving, or a patch breaks down after seeming to heal — especially on the lower legs, where healing is slower.

One to three months — the follow-up that matters

Residual pinkness fades over weeks; occasionally pigment change (darker or lighter patches) persists longer. Around 6–8 weeks after finishing, the treated area is reviewed to confirm clearance, deal with anything left behind, and set up ongoing surveillance — field treatment reduces future risk, it does not remove the need for regular skin checks. ^(2,5)

Any lesion that persists, regrows or ulcerates after treatment needs review rather than another round of cream on your own initiative.

Before you start — or if you’re mid-course and unsure

A 20-minute review is enough to check the reaction, adjust the plan if needed, or talk through whether Efudix or an alternative field treatment suits you better.

Related reading

• Efudix (5-fluorouracil) — full patient guide →
• Efudix vs Aldara vs PDT — choosing a field treatment →
• What is field cancerisation? →