Sunscreens: essential to prevent skin cancer, but how to choose them well?
UVA/UVB, SPF 30 vs 50, organic and mineral filters, nanoparticles, vitamin D: what science says for effective photoprotection.
Doctor Florian A. Vallecillo Cabrera
Author
Sunscreens effectively reduce sunburn, photo-ageing and the risk of skin cancers. Choosing them well (SPF 50+, suitable filters) and applying them correctly matters more than the debate over filters. The best strategy combines clothing, shade and cream — never a « permit to tan ».
Summary
The sun is essential to life. It contributes to vitamin D synthesis, influences our biological rhythm and improves psychological well-being. But it is also the main environmental factor responsible for premature skin ageing and the majority of skin cancers.
Sun protection is today an essential prevention tool. However, it should not be seen as permission to stay in the sun longer.
When used properly, it effectively reduces damage caused by ultraviolet rays. The potential risks raised about certain sunscreen filters remain, to date, far lower than the clearly demonstrated risks of excessive UV exposure.
Why does the sun damage the skin?
Solar radiation is made up of several types of ultraviolet.
UVB
They represent about 5% of the UV reaching the Earth. They act mainly at the level of the epidermis. They are responsible for:
- sunburn;
- skin burns;
- part of the DNA mutations that can lead to skin cancer.
They are what mainly determine the SPF index.
UVA
UVA represent about 95% of ultraviolet. They penetrate much more deeply into the skin. They are mainly responsible for:
- skin ageing;
- wrinkles;
- pigment spots;
- loss of elasticity;
- part of skin cancers.
Unlike UVB, they pass through clouds and glass. They are present all year round.
Is the sun entirely bad?
No. Reasonable exposure has several benefits:
- vitamin D synthesis;
- regulation of the biological clock;
- improved mood;
- contribution to bone metabolism.
The problem is therefore not the sun itself, but excessive exposure, particularly repeated sunburns.
Why should you protect yourself?
Ultraviolet causes progressive DNA damage. Our body is able to repair some of it. However, over the years, these lesions accumulate. They promote:
- basal cell carcinoma;
- squamous cell carcinoma;
- melanoma;
- premature skin ageing.
It is estimated that about 80% of the visible ageing of the face is linked to the sun, a phenomenon called photo-ageing.
How do sunscreens work?
All sunscreens work by reducing the amount of UV radiation reaching the skin. Two main families of filters are distinguished.
Organic filters (formerly called chemical)
These molecules absorb ultraviolet rays and transform them into a small amount of heat. They are very effective, invisible after application, easy to spread and widely used in modern creams. The filters currently authorised in Europe have undergone rigorous safety assessments.
Mineral filters
They mainly contain zinc oxide and titanium dioxide. Contrary to a long-held belief, they do not work only as mirrors. Studies show that they also absorb a large part of UV radiation while reflecting a small proportion. They are often recommended:
- in infants when sun protection is necessary;
- in some people allergic to organic filters;
- after certain skin treatments.
Are sunscreen filters dangerous?
This question comes up very often. To date, the benefits of photoprotection far outweigh the potential risks associated with authorised filters. Some molecules can be found in very small amounts in the blood after application. This does not mean they are toxic.
European health agencies continue to assess their safety regularly. Some older molecules have been withdrawn or limited when doubts existed. Surveillance is permanent.
Are mineral filters containing nanoparticles dangerous?
Nanoparticles regularly raise questions. Current scientific data show that:
- they do not significantly penetrate healthy skin;
- they remain essentially on the surface of the skin;
- they are considered safe in creams when they comply with European regulations.
On the other hand, their use in spray form is more strictly regulated to avoid inhalation.
Do sunscreens prevent vitamin D production?
No. In real life, no study has shown that normal use of a sunscreen systematically caused vitamin D deficiency. In practice, creams are never applied perfectly, some areas remain uncovered and a small amount of UV always reaches the skin. Most people therefore continue to synthesise vitamin D despite sun protection.
What is the difference between SPF 30 and SPF 50?
SPF mainly measures protection against UVB. In theory, SPF 30 blocks about 97% of UVB and SPF 50 about 98%. The difference seems small. Yet in:
- very fair skin;
- children;
- people who have already had skin cancer;
- patients on photosensitising treatments,
SPF 50 remains preferable because it offers a better safety margin when the applied amount is insufficient.
How much should be applied?
Most people apply only 25 to 50% of the necessary amount. For an adult, you need approximately:
- one teaspoon for the face and neck;
- one teaspoon for each arm;
- two teaspoons for each leg;
- two teaspoons for the trunk.
The cream should be reapplied every two hours and after each significant swim or heavy sweating.
Does clothing protect better than cream?
Yes. Clothing is the most effective protection. The best means of prevention remain:
- seeking shade;
- wearing a wide-brimmed hat;
- wearing UV-filtering glasses;
- wearing covering clothes;
- avoiding exposure between 12 pm and 4 pm in summer.
Sunscreen complements these measures but does not replace them.
Do children need particular protection?
Absolutely. Childhood sunburns increase the risk of melanoma in adulthood. In young children:
- avoid direct exposure as much as possible;
- favour anti-UV clothing;
- use suitable SPF 50+ protection when exposure is unavoidable.
Common misconceptions
« I'm tanned, I no longer need protection. »
False. A tan corresponds only to very weak protection.
« On a cloudy day, I'm not at risk. »
False. Up to 80% of UV pass through clouds.
« An SPF 100 cream protects twice as much as SPF 50. »
False. The real difference is very small.
« A single application is enough for the whole day. »
False. Sweating, rubbing and swimming gradually reduce protection.
« Dark skin does not get skin cancer. »
False. The risk is lower but it exists. Cancers are often diagnosed later.
Sun protection and the environment
Some molecules used in sunscreens are currently the subject of research into their environmental impact, particularly on marine ecosystems. In some regions of the world, such as Hawaii, a few specific filters have been banned as a precaution. Research continues to develop ever more effective and more environmentally friendly filters. To date, this does not call into question the need to protect the skin effectively against UV.
Valorian's recommendations
At Valorian, we recommend intelligent photoprotection:
- avoid prolonged exposure;
- seek shade when possible;
- wear covering clothes;
- use an SPF 50+ sunscreen suited to your skin type;
- reapply regularly;
- protect children in particular;
- have a regular medical skin check in the presence of many moles or a personal or family history of skin cancer.
The Valorian analysis
Sun protection is today one of the most effective prevention measures for the skin. Its effectiveness in reducing sunburn, limiting photo-ageing and lowering the risk of skin cancers is solidly demonstrated by scientific studies.
The questions concerning certain UV filters must be put into context. Health authorities regularly reassess their safety and adapt regulations when necessary. To date, no data justifies giving up photoprotection because of these concerns.
At Valorian, we favour a holistic approach: the best strategy is to combine clothing, seeking shade, limiting exposure during the most intense hours and correct use of suitable sun protection. Sunscreen should never be seen as a « permit to tan », but as an essential element of reasoned prevention.
Key points
- ◆UVB mainly cause sunburn and mutations; UVA (95% of UV) penetrate deeper and cause photo-ageing and spots, all year round.
- ◆The benefit of photoprotection far outweighs the potential risks of authorised filters, continuously reassessed by European authorities.
- ◆SPF 50+ is preferable for fair skin, children and a history of skin cancer; people usually apply only 25–50% of the needed dose.
- ◆Clothing, shade and avoiding 12 pm–4 pm protect better than cream alone, which complements them.
- ◆Sunscreen does not prevent vitamin D synthesis and is never a « permit to tan ».
Valorian level of evidence
- Scientific quality(5/5)
The recommendations are based on data from the WHO, EADV, AAD, the Société Française de Dermatologie and European authorities.
- Current clinical application(5/5)
Photoprotection is one of the most effective and best-validated preventive interventions for reducing skin cancers and premature skin ageing.
- Future potential(4/5)
Research continues to improve UV filters, their tolerance and their environmental impact, but the fundamental principle remains: the best sunscreen is the one that is correctly applied and combined with physical protection measures against the sun.
References
- Organisation Mondiale de la Santé (OMS).
- American Academy of Dermatology (AAD).
- European Academy of Dermatology and Venereology (EADV).
- Société Française de Dermatologie.
- Comité scientifique européen pour la sécurité des consommateurs (SCCS) — évaluations européennes en vigueur sur la sécurité des filtres UV.
Frequently asked questions
SPF 30 or 50?
SPF 30 blocks ~97% of UVB and SPF 50 ~98%. The theoretical gap is small, but SPF 50+ is preferable for fair skin, children, a history of skin cancer and photosensitising treatments, because people often apply too little cream.
Are sunscreen filters dangerous?
To date, the benefits of photoprotection far outweigh the potential risks of authorised filters. European authorities continuously reassess their safety and withdraw doubtful molecules.
Does sunscreen prevent vitamin D production?
No. In practice, application is never perfect, some areas stay uncovered and some UV always reaches the skin: most people continue to synthesise vitamin D.
How much and how often?
About one teaspoon per area (face/neck, each arm) and two for each leg and the trunk, reapplied every 2 hours and after swimming or heavy sweating.
