Ingredient Beauty BenefitsUV filter · An ingredient class — not a single line on an ingredient list
Sunscreen: squamous cell carcinoma went down, basal cell carcinoma did not
An Australian trial randomised 1,621 people and followed them 4.5 years. Squamous cell tumour incidence was 39% lower (1,115 vs 1,832 per 100,000); basal cell carcinoma showed no difference. This is one of the few entries on this site carrying strong evidence.
Last checked Sep 16, 2026
Start here
- What it is
Not a single ingredient but a class. What this page covers is not one raw material but the act of applying sunscreen daily.
- What it is used for
Reducing the pigment, wrinkling and skin-cancer risk that come from ultraviolet light.
- How it is said to work
It is said to absorb or reflect ultraviolet, reducing how much reaches the skin. This is one of the few items on this site carrying 'strong evidence'.
There are no numbers and no citations in this box. What has been established, and how far, is below.
At a glance
- In pregnancy
- No specific restriction
- Irritation
- Low
- Daytime use
- ✓ Fine
- How well established
- Strong evidence
- Concentration studied
- Not disclosed
- Length of the studies
- 234 weeks
Not a measurement — reported irritation grouped into five steps. It varies between people.
“Concentration studied” and “Length of the studies” are taken straight from the research on this page. They are not a recommended dose, and the figure for each finding is written out in the text.
This is not how large the effect is but how well confirmed it is. It shows the highest grade among the findings on this page.
Sunscreen carries the firmest evidence on this site. Almost all of it comes from one trial.
In 1992, in the town of Nambour in Queensland, Australia, 1,621 residents were randomised: one group applied SPF 15+ to head, neck, arms and hands every day, the other used sunscreen as they normally would. That single trial produced three papers — skin cancer in 1999, melanoma in 2011, photoageing in 2013. Three papers, one trial.
This is also not an ingredient but an ingredient class. What the evidence attaches to is not zinc oxide or any single filter but the act of applying sunscreen daily. You will not find this name on an ingredient list.
Contents
What is established
The same ingredient at a different strength, in a different formula, is a different product. These are the conditions the studies used.
Squamous cell tumour incidence was 39% lower
Over 4.5 years, 1,383 participants had full skin examinations by a dermatologist; 250 of them developed 758 new skin cancers.
Counted as tumours, squamous cell carcinoma occurred at 1,115 per 100,000 in the daily group against 1,832 in the discretionary group — a ratio of 0.61 (95% CI 0.46 to 0.81). That difference is clear.
Counted as people developing a first new cancer, however, squamous cell carcinoma showed no significant difference either (876 vs 996; 0.88 [0.50 to 1.56]). What fell was the number of tumours, not the number of people affected. The two numbers tell different stories, and this entry rests on the second one.
- Randomised controlled trial in people · 1,621 participants · 234 weeks · Compared with usual (discretionary) use · Funding not declared · Endpoint clinical events (cancers, lesion counts) PMID 10475183 · abstract read
Basal cell carcinoma did not go down
In the same trial, basal cell carcinoma showed no difference on any measure. First new cancers ran at 2,588 versus 2,509 per 100,000 (ratio 1.03, 95% CI 0.73 to 1.46), and counting tumours showed no effect either.
Basal cell carcinoma is the most common skin cancer there is. The sentence 'sunscreen prevents skin cancer' does not survive this result intact.
A properly designed randomised trial finding no difference is the best kind of evidence for 'not established'. This is not an absence of research; the research was done and nothing came out.
- Randomised controlled trial in people · 1,621 participants · 234 weeks · Compared with usual (discretionary) use · Funding not declared · Endpoint clinical events (cancers, lesion counts) PMID 10475183 · abstract read
Melanoma halved, but the statistics were borderline
This comes from follow-up to 2006, ten years after the trial ended. Eleven new melanomas occurred in the daily sunscreen group against 22 in the discretionary group — hazard ratio 0.50 (95% CI 0.24 to 1.02), P = .051.
The confidence interval crosses 1 and the P value sits just above .05. This result is widely quoted as 'sunscreen halved melanoma'; by the trial's own standard it was not significant.
Restricted to invasive melanoma the gap was wider, 3 against 11. But with counts that small, chance has correspondingly more room.
- Randomised controlled trial in people · 1,621 participants · Compared with usual (discretionary) use · Funding not declared · Endpoint clinical events (cancers, lesion counts) PMID 21135266 · abstract read
After 4.5 years there was 24% less skin ageing
In the same town, 903 adults under 55 had the microtopography of their skin surface graded from 1992 and 1996 casts by assessors blinded to their group.
The daily sunscreen group showed no detectable increase in skin ageing over 4.5 years, and 24% less than the discretionary group (relative odds 0.76, 95% CI 0.59 to 0.98).
The β-carotene supplement tested alongside had no effect on skin ageing at all.
This entry is moderate rather than strong because there is one trial. Most anti-ageing ingredients do not have even this.
- Randomised controlled trial in people · 903 participants · 234 weeks · Compared with usual (discretionary) use · Funding not declared · Endpoint scores from blinded assessors PMID 23732711 · abstract read
Korea lists 28 UV filters, each with a maximum concentration
Annex 4, item 1 of the Regulation on the Review of Functional Cosmetics sets out UV filters and their maximum concentrations — zinc oxide and titanium dioxide at 25%, octocrylene and homosalate at 10%, ethylhexyl methoxycinnamate at 7.5%, and so on.
These are ceilings, not recommendations. And SPF is determined by testing on people, not calculated from the formula, so an ingredient list will not tell you the protection factor.
UV protection is one of the functional categories in Article 2(5) of the Enforcement Rule of the Cosmetics Act.
How to use it
- The trial used it daily. Applying only on bright days is a different intervention from the one that was tested.
- The result applies to the areas covered. Nambour participants applied it to head, neck, arms and hands, and the analysis counted only cancers arising there.
- SPF is measured on people, using 2 mg per cm² in the laboratory. Few people apply that much.
- Use it especially while you are using retinol or exfoliating acids.
Cautions
- The trial ran in Queensland, Australia. Whether the result transfers to different UV levels and skin types is a separate question.
- Wearing sunscreen is not permission to stay out longer. The trial did not ask anyone to increase their exposure.
- There is ongoing discussion about systemic absorption of some organic filters. Absorption being demonstrated and harm being demonstrated are different things, and the second has not been.
With a new ingredient, apply a small amount somewhere inconspicuous, such as the inner arm, for two days first. Stop if it reddens or stings.
Related skin concerns
What this article relies on
Unless marked otherwise, a paper was read to the abstract. Only papers whose full text we opened are marked as such.
- 기능성화장품 심사에 관한 규정 [별표 4] 자료제출이 생략되는 기능성화장품의 종류 — 식품의약품안전처고시 제2025-88호식품의약품안전처 · 시행 2025-12-16 · Checked on 2026-09-16
- 화장품법 시행규칙 제2조(기능성화장품의 범위) — 총리령 제2109호식품의약품안전처 · 시행 2026-04-02 · Checked on 2026-09-16
- PubMed — 미국 국립의학도서관 문헌 데이터베이스National Library of Medicine · Checked on 2026-09-16