Sunscreen and the Healthy Tennis Player
Young Ju, Ph.D.
As Summer approaches, most of us will use sunscreens to protect against the harmful effects of ultraviolet (UV) radiation from sunlight, including skin cancer. Many formulations of sunscreen are available today which can be confusing to the consumer. This article is intended to help you make informed decisions by answering these questions:
What do these products contain?
How do they work?
What do SPF numbers mean?
Are they safe?
The Spectrum of Sunlight
There are several types of rays from sunlight including ultraviolets (UVs), visible, and infrared light based on their respective wavelengths that have specific actions and effects on your skin (1).
The ozone layer serves to protect the Earth from harmful UV radiation, but ozone layer depletion alters the amounts of UV radiation that is blocked. Both UVA and UVB forms of ultraviolet light contribute to the development of skin cancer (see July 2023 article on skin cancer). Therefore, protecting the skin from both UVB and UVA rays is increasingly important.
Ingredients in Sunscreens
The history of sunscreen use goes back to around 4000 BC in Egypt (2). The Egyptians applied a paste of rice, jasmine, and lupine to their skin for sun protection. In ancient Greece, athletes applied a mixture of oil and sand (which could have provided zinc oxide). These ingredients are still found in sunscreens today.
In the US, the US Food and Drug Administration (FDA) considers sunscreens to be over-the-counter drugs and regulates them to meet effectiveness and safety standards. The FDA-approved sunscreens vary in their composition and mechanism of action. Typically, commercially available sunscreens contain 10-20% of UV filter(s) (3).
The FDA has approved 16 UV filters. They can be categorized into two main types: inorganic (physical or mineral) and organic (chemical) filters (3, 4):
Inorganic ingredients (e.g., titanium dioxide, zinc oxide) create a physical barrier on the skin that reflects and scatters UVA and UVB rays before absorption. They are immediately effective after being applied, tend to be thicker, and are tolerated better by people with sensitive skin.
Organic ingredients absorb UV rays by changing their chemical structure before they can damage the skin. They need to be applied 15-20 minutes before sun exposure. They are generally more lightweight and absorbent, but they wear off more quickly requiring reapplication and can be irritating for sensitive skin.
UVA blockers (e.g., avobenzone, meradimate)
UVB blockers (e.g., octisalate, octinoxate, octocrylene, homosalate, oxybenzone)
Broad-Spectrum blockers block both UVA and UVB light (e.g., dioxybenzone, ecamsule)
Various formulations are available. Some products are inorganic filter-based, some are organic filter-based (either single filter or multiple filters), and others are a combination of inorganic and organic filters. Sunscreens also contain other components beyond UV filters, including emollients to soften and hydrate, thickeners to increase the viscosity, preservatives, stabilizers, fragrances, etc. You can find the UV filter information in a Drug Facts panel on sunscreen products.
Some potential health concerns (5) have been raised about some organic filters like oxybenzone, octinoxate, and homosalates, including hormone disruption in rodents (6) and detectable levels in blood, milk, and urine in humans (7, 8). These findings guarantee a benefit-risk assessment of UV filters. The FDA has requested data from industry to confirm the safety of these ingredients. So far, there is no conclusive research evidence that these chemicals are harmful to humans at the doses in sunscreen use. However, there is increasing evidence of harmful environmental effects caused by UV filters, including coral bleaching. Some areas, including Hawaii, Palau, Key West, and the US Virgin Islands, have banned sunscreens containing certain organic filters (e.g., oxybenzone and octinoxate) to protect coral reefs and marine ecosystems. If you travel to those areas, inorganic-based sunscreens are recommended.
Sunscreen comes in many forms, including lotions, creams, sticks, gels, oils, pastes, sprays. All forms work well when you follow the application directions on the Drug Facts panel, you can choose a product suitable to your preferences. For example, sprays can be difficult to apply evenly, can be accidentally inhaled, and can cause irritation for some people (e.g., with respiratory conditions).
Sun Protection Factor (SPF) (9, 10)
The SPF numbers indicate how much protection is provided from UVB rays. (The SPF category description differs from one country to another.)
SPF 15: blocks ~93% of UVB rays
SPF 30: blocks ~97%
SPF 50: blocks ~98%
SPF 100: blocks ~99%
SPF 30 is ideal for every day and occasional sun exposure. The Skin Cancer Foundation (11) grants the “Daily Use” seal to sunscreens that provide protection against sun exposure for short periods.
SPF 50 or higher is ideal for extended outdoor activities, including outdoor sports. Look for “Active” seal of recommendation.
Water-resistant and very water-resistant products are for swimming or intense exercise up to 40 minutes and 80 minutes in the water, respectively. There is no completely waterproof sunscreen.
While SPF indicates only UVB protection, a broad-spectrum formula provides protection against both UVB and UVA rays.
The UV Index predicts the UV radiation levels on a 1-11+ scale, helping people determine appropriate sun-protective behaviors, such as sunglasses, hats, sunscreens, long sleeves or shade. The UV index is calculated by the National Weather Service and published by the Environmental Protection Agency. You can access the UV Index (12) to see whether extreme conditions warrant such protection.
Here are some general safety tips for sun and sunscreen (13):
Limit sun exposure when the sun rays are most intense, especially between the hours of 10 am and 2 pm.
Wear long-sleeved shirts, pants, sunglasses, and broad-brimmed hats when you can.
Use broad-spectrum sunscreens with SPF 30 or higher for everyday activities.
Reapply sunscreen at least every 2 hours if you are sweating a lot or swimming.
Do not use sunscreens for infants under 6-months old.
Do not expose sunscreen containers to direct sun.
Discard expired sunscreens that may not be safe and effective anymore.
Wash off sunscreen at the end of the day or after outdoor activity as they could clog pores and irritate skin.
Conclusion
UV exposure is strongly associated with skin cancer and premature skin aging. Depending on your activity level, skin type, and preferences, you can find a sunscreen suitable for you that protects against harmful UV radiation. As always, I recommend reading the Drug Facts panel to see the active/inactive ingredients as well as uses, warnings, and directions.
Dr. Young Ju is a Ph.D and Associate Professor of Human Nutrition, Foods, and Exercise at Virginia Tech.
References
U.S. Environmental Protection Agency. https://www.epa.gov/enviro/uv-index-overview
Ma et al. “History of sunscreen: An updated view” J. Cosmet Dermatol. 2021, 20:1044.
NIH. National Library of Medicine National Center for Biotechnology Information. “2. Introduction to sunscreens and their UV filters” https://www.ncbi.nlm.nih.gov/books/NBK587270/
Latha et al. “Sunscreening agent” J Clin Aesthet Dermatol. 2013, 6(1):16.
Breakell et al. “Ultraviolet filters: Dissecting current facts and myths” J. Clin. Med. 2024, 13(10):2986.
Klammer et al. “Effects of a 5-day treatment with the UV-filter octylmethoxycinnamate (OMC) on the function of the hypothalamo-pituitary-thyroid function in rats” Toxicology. 2007, 238 (2-3):192.
Krause et al. “Presence of benzophenones commonly used as UV filters and absorbers in paired maternal and fetal samples.” Environ. Int. 2018, 110:51.
Schlumpf et al. “Exposure patterns of UV filters, fragrances, parabens, phthalates, organochlor pesticides, PBDEs, and PCBs in human milk: correlation of UV filters with use of cosmetics.” Chemosphere. 2010, 81:1171.
American Academy of Dermatology Association. “Sunscreen FAQs” https://www.aad.org/media/stats-sunscreen
Skin Cancer Foundation. “All about sunscreen” https://www.skincancer.org/skin-cancer-prevention/sun-protection/sunscreen/
Skin Cancer Foundation. “Seal of Recommendation” https://www.skincancer.org/skin-cancer-prevention/seal-of-recommendation/
US Environmental Protection Agency. “UV Index Description” https://www.epa.gov/enviro/uv-index-description#:~:text=The%20UV%20Index%20provides%20a,much%20sun%20can%20be%20dangerous
US Food and Drug Administration “Sunscreen: How to help protect your skin from the sun”https://www.fda.gov/drugs/understanding-over-counter-medicines/sunscreen-how-help-protect-your-skin-sun#:~:text=Higher%20SPF%20values%20(up%20to,SPF%20of%20at%20least%2015.
This information is provided for your reference and you use at your own risk; you should rely on your medical professional for medical advice.
