Will field therapy make my skin red and sore?

Usually, yes — and that is expected. Effective topical field treatments work by provoking a controlled inflammatory reaction as they clear abnormal cells, so redness, scaling and crusting for one to several weeks is normal. The intensity tends to reflect how much sun damage is present.

How often do I need field therapy?

It depends on the severity of your sun damage and your ongoing UV exposure. Some patients need a "clear-out" every 1–2 years; others go longer between courses if they maintain strict daily sun protection. Your plan is individualised at review.

Can I do field therapy in summer?

It can be done year-round, but treated skin is temporarily very sensitive to UV, so many patients prefer the cooler months. If treated in summer, strict sun avoidance during healing is essential.

Which field treatment is best?

It depends on the area, lesion thickness, your skin type and how much downtime you can manage. In a head-to-head randomised trial, 5% fluorouracil (Efudix) was the most effective of four field treatments for actinic keratosis on the head. Laser-assisted PDT suits extensive damage or patients who prefer an in-clinic option. We match the approach to you.

Field therapy

Treating sun damage to prevent future skin cancers (field therapy)

When we treat one skin cancer we are pulling a single "weed." For many patients the surrounding skin is also sun-damaged and holds invisible precancerous change — "field cancerisation." Field therapy treats the whole at-risk area to clear it and lower the chance of future cancers. This page covers spot vs field treatment and the evidence for Efudix, Aldara and laser-assisted PDT.

By Dr Christopher Irwin, MBChB, FRACGP, MMed (Skin Cancer), FACAM, MSCCA

Last reviewed 2026-06-06 · 6 min read · Editorial policy

In brief

Field cancerisation describes surrounding skin that received the same lifetime UV dose and carries the same mutations.
Spot treatment (e.g. cryotherapy) targets only visible lesions; field treatment targets the whole at-risk zone.
In a randomised trial of four field treatments, 5% fluorouracil (Efudix) was the most effective for actinic keratosis on the head.
Aldara (imiquimod) works by activating the local immune system to clear sun-damaged cells.
Laser-assisted photodynamic therapy can clear extensive damage in one or two in-clinic sessions.
Field therapy aims to reduce future cancer risk, break the treatment cycle and make surveillance easier.
Even normal-looking field skin carries UV-induced DNA mutations prone to forming future tumours.
Efudix runs as a 2-4 week course that triggers a vigorous, expected healing reaction.
Suspicious lesions are biopsied before field therapy begins.
Treatment is matched to the area, lesion thickness, skin type and downtime you can manage.

Quick summary

Treating one skin cancer is like pulling a single weed. For many patients the surrounding skin — the “soil” — is also sun-damaged and holds invisible precancerous change, a concept called field cancerisation. ⁽¹⁾ Field therapy treats the whole at-risk area to clear that sub-clinical damage and lower the chance of new cancers. The main options are topical 5-fluorouracil (Efudix), topical imiquimod (Aldara), and laser-assisted photodynamic therapy (PDT) — matched to the area, lesion thickness, skin type and downtime you can manage.

When we treat a single skin cancer, we are effectively pulling one “weed.” But for many patients the surrounding skin is also heavily sun-damaged and contains invisible, precancerous changes. Field therapy treats an entire area — such as the face, scalp or backs of the hands — to clear this sub-clinical damage and significantly lower the chance of future cancers forming.

Related reading:

What is field cancerisation?

If you have had an actinic keratosis or a squamous cell carcinoma, the skin around that lesion has usually received the same cumulative lifetime UV dose — creating a “field” of cells at various stages on the path to cancer. ⁽¹⁾

Even when this skin looks normal, the cells carry UV-induced DNA mutations that make them prone to forming future tumours. Treating only the visible spots while ignoring the surrounding field often leads to a cycle where new lesions appear soon after the last ones are removed. ⁽¹⁾

Spot treatment vs field treatment

Most patients know “freezing” individual spots with liquid nitrogen (cryotherapy). It is effective for visible, thicker lesions, but does nothing for the surrounding damaged skin.

Spot treatment targets only what is visible today. It does not prevent new cancers in the adjacent skin.
Field treatment targets the whole at-risk zone, reducing the frequency of future surgeries and repeated spot treatments.

Topical field treatments

Several prescription creams seek out and destroy precancerous cells while largely sparing healthy skin. They are often the first line in a prevention strategy. ⁽²⁾

Efudix (5-fluorouracil)

Efudix (5-fluorouracil) targets rapidly dividing precancerous cells, typically over a 2–4 week course that triggers a vigorous, expected “healing reaction.” In a randomised head-to-head trial of four field treatments for actinic keratosis on the head, 5% fluorouracil was the most effective, with the highest proportion of patients remaining free of treatment failure at 12 months. ⁽²⁾

Aldara (imiquimod)

Aldara (imiquimod) works by activating the local immune system to recognise and clear sun-damaged cells. It can be a useful option where an immune-driven approach suits the lesion pattern and location. ⁽²⁾

Laser-assisted photodynamic therapy (PDT)

For extensive damage, or for patients who prefer to avoid weeks of cream, laser-assisted PDT is often the preferred in-clinic option. A light-sensitising medication is applied and then activated with a controlled light source, destroying sun-damaged cells — often in one or two sessions — and frequently improving overall skin texture as well.

The preventative benefit

The goal of field therapy is to “reset” the skin and lower future risk. By clearing the field of actinic keratoses we aim to:

lower future cancer risk — actinic keratoses are markers of a field that can give rise to invasive squamous cell carcinoma ⁽¹⁾
break the cycle of repeated cryotherapy and surgical excisions
make surveillance easier — once the “background noise” of sun damage is cleared, new suspicious changes are easier to spot at your regular skin checks

Book an assessment

Book a field therapy consultation Actinic keratosis treatment

Frequently asked questions

Will field therapy make my skin red and sore?

Usually, yes — and that is expected. Effective topical field treatments work by provoking a controlled inflammatory reaction as they clear abnormal cells, so redness, scaling and crusting for one to several weeks is normal. The intensity tends to reflect how much sun damage is present.
How often do I need field therapy?

It depends on the severity of your sun damage and your ongoing UV exposure. Some patients need a "clear-out" every 1–2 years; others go longer between courses if they maintain strict daily sun protection. Your plan is individualised at review.
Can I do field therapy in summer?

It can be done year-round, but treated skin is temporarily very sensitive to UV, so many patients prefer the cooler months. If treated in summer, strict sun avoidance during healing is essential.
Which field treatment is best?

It depends on the area, lesion thickness, your skin type and how much downtime you can manage. In a head-to-head randomised trial, 5% fluorouracil (Efudix) was the most effective of four field treatments for actinic keratosis on the head. Laser-assisted PDT suits extensive damage or patients who prefer an in-clinic option. We match the approach to you.

References

Related treatments

By Dr Christopher Irwin, MBChB, FRACGP, MMed (Skin Cancer), FACAM, MSCCA

Last reviewed 2026-06-06 · Editorial policy