Can your skin learn to handle the sun on its own?
Some voices on social media and on television say that sunscreen does more harm than good, that the skin gets used to the sun if you build up slowly, and that the sun is not what causes skin cancer. Every summer, others say the opposite. So what do the studies actually show?
The claim
The idea comes in several versions. One is that the sun is not what causes skin cancer [1]. Another is that the skin can adapt to the sun through gradual exposure, building up a kind of natural protection sometimes called a "sun callus" [2]. A third questions the need for sunscreen altogether [3].
Where it came from
The idea builds on real facts. Small amounts of ultraviolet radiation are good for health, because the skin needs them to make vitamin D [4]. The skin does respond to the sun by tanning and by appearing to thicken [2]. And in 2020, a trial by researchers at the US medicines regulator found that the active ingredients of several sunscreens are absorbed into the blood [5].
Who promotes it
Spanish footballer Marcos Llorente has called the idea that sun exposure causes skin cancer a fallacy. In April 2026 he posted on Instagram a mock sunscreen bottle that read "Protection against your biology" and "Blocking Vitamin D since 1985" [1].
In the United States, television personality Kristin Cavallari said on her podcast Let's Be Honest in early 2024 that she does not wear sunscreen. Months later she clarified that she had never told anyone else not to wear it [3].
Where it spreads today
In April 2026, Spain's medicines agency (AEMPS) issued a statement to refute the "sun callus", noting that the myth had recently spread on social media and other digital channels [2].
The trend is not only Spanish. In a May 2026 survey, the American Academy of Dermatology found that nearly half of Americans, and 64% of 18-to-29-year-olds, said they had come across sunscreen misinformation online, and that more than 16 million adults said they had cut back on or stopped using sunscreen because of online claims [6].
What the evidence says
The International Agency for Research on Cancer, part of the World Health Organization, classifies solar radiation as carcinogenic to humans (Group 1), its highest category [7]. According to the WHO, excessive exposure to ultraviolet radiation caused around 1.2 million non-melanoma skin cancers and 325,000 melanomas worldwide in 2020 [4].
The skin does not learn to protect itself. The AEMPS explains that tanning and the apparent thickening of the skin are biological responses to damage caused by ultraviolet radiation, not safe protection; that there is no scientific evidence that the skin can get used to the sun through gradual exposure; and that every unprotected exposure adds to the damage [2].
Sunscreen helps. In a randomised trial in Nambour, Australia, 1,621 adults applied sunscreen either daily or at their own discretion between 1992 and 1996. Ten years later, the daily group had half as many new melanomas (11 against 22), a difference just short of statistical significance, and about a quarter as many invasive melanomas, the kind that spreads (3 against 11) [8].
The 2020 absorption study warned that its results "do not indicate that individuals should refrain from the use of sunscreen" [5]. As for vitamin D, a 2019 review found little evidence that sunscreen lowers vitamin D levels when used in real life, although no trials had yet tested the high-protection sunscreens now recommended [9].
Sunscreen is not the first line of defence either. The WHO recommends limiting time in the midday sun, seeking shade and wearing clothing, a hat and sunglasses, using sunscreen on the skin clothes cannot cover, and never using it to stay longer in the sun [4]. The European Code Against Cancer sums it up: "Avoid too much sun exposure, especially for children. Use sun protection. Never use sunbeds" [10].
Evidence behind this entry
Distinct sources cited, by tier.
| Tier 1: Systematic reviews and official positions | 5 |
|---|---|
| Tier 2: Studies, rulings and records | 2 |
| Tier 3: Journalism and expert organizations | 3 |
| Tier 4: Claim sources | 0 |
Verdict
The sun is the main cause of skin cancer, and the skin does not build up a protective "callus": a tan is a sign of damage. Sunscreen is not a licence to bake for hours, nor the only protection; shade, clothing and avoiding the midday sun come first. But for the skin you cannot cover, it works, and the studies give no reason to give it up.
Sources
Tier 1: Systematic reviews and official positions
- 2. La AEMPS desmiente el «callo solar» y recuerda la importancia de una exposición solar segura (COS, 09/2026). Agencia Española de Medicamentos y Productos Sanitarios (AEMPS), 2026-04-21. aemps.gob.es
- 4. Ultraviolet radiation (fact sheet). World Health Organization, 2022-06-21. who.int
- 7. Radiation. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 100D. International Agency for Research on Cancer (IARC/WHO), 2012. publications.iarc.who.int
- 9. The effect of sunscreen on vitamin D: a review. British Journal of Dermatology (Neale RE, Khan SR, Lucas RM, et al.), 2019-11. doi:10.1111/bjd.17980
- 10. European Code Against Cancer, 5th edition. International Agency for Research on Cancer (IARC/WHO) and European Commission, 2025. cancer-code-europe.iarc.who.int
Tier 2: Studies, rulings and records
- 5. Effect of Sunscreen Application on Plasma Concentration of Sunscreen Active Ingredients: A Randomized Clinical Trial. JAMA (Matta MK, Florian J, Zusterzeel R, et al.), 2020-01-21. doi:10.1001/jama.2019.20747
- 8. Reduced melanoma after regular sunscreen use: randomized trial follow-up. Journal of Clinical Oncology (Green AC, Williams GM, Logan V, Strutton GM), 2011-01-20. doi:10.1200/JCO.2010.28.7078
Tier 3: Journalism and expert organizations
- 1. Marcos Llorente posts controversial sun cream costume: 'Against your biology'. Football España (Jonatan Vazquez), 2026-04-03. football-espana.net
- 3. Kristin Cavallari shuts down claims she told people not to use sunscreen after taking heat for viral clip. Fox News (Brie Stimson), 2024-07-31. foxnews.com
- 6. Misinformation puts over 16 million Americans at an increased risk for skin cancer. American Academy of Dermatology, 2026-05-01. newswise.com