With UV radiation peaking during summer months and between 10 AM and 4 PM, protecting your skin from sun damage is essential. But with increasing concern over sunscreen ingredients and hormonal health, many are left wondering—what’s safe and effective?
Understanding UV Radiation
UV radiation (UVR) is categorized into UVA, UVB, and UVC. UVC has the potential to cause the most damage to our skin. Fortunately, almost all of it is blocked by the ozone layer. UVB mainly affects the most superficial layer of skin, the epidermis, causing sunburn and DNA damage. Two positive effects of UVB are that it facilitates vitamin D production and has immunosuppressive effects, hence the role of phototherapy in the treatment of inflammatory skin conditions, including psoriasis. UVA penetrates deeper into the dermal layer of the skin, accelerating aging. Windows and clouds filter less UVA compared to UVB, so it’s important to remember to protect exposed skin even on cloudy days and on long road trips in the car.
How Sunscreens Work
Ultraviolet radiation (UVR) was first discovered in 1801 by Johann Wilhelm Ritter. In the 1920s, scientists Karl Eilham Hausser and Wilhelm Vahle demonstrated that UVA exposure causes tanning, while prolonged UVB exposure leads to sunburn—findings that led to the development of the first commercial sunscreens containing UVB-filtering compounds like benzyl salicylate and benzyl cinnamate. Decades later, in 1969, dermatologist Albert Kligman identified the photoaging effects of UVA rays and stressed the importance of UVA protection, prompting the development of avobenzone as the first UVA-specific sunscreen filter.
- Organic (chemical) filters absorb UV rays and convert them to heat. Common ingredients include oxybenzone, avobenzone, and homosalate. A filter is considered organic if it is carbon‐based. This terminology does not equate to ‘natural’ nor do these filters decompose naturally in the environment.
- Inorganic (mineral) filters like zinc oxide and titanium dioxide reflect and scatter UV rays, which give them a more apparent appearance when applied to the skin surface.
Hormonal and Endocrine Considerations
- Ingredients like oxybenzone and octinoxate have shown estrogenic or anti-androgenic effects in lab and animal studies. They’re systemically absorbed and may persist in the bloodstream.
- Human studies remain inconclusive, but concern persists about endocrine and thyroid disruption.
- Mineral sunscreens show minimal absorption and are preferred for hormone-conscious individuals.
Hormone Replacement Therapy (HRT) & UV Sensitivity
- Topical estrogens may increase melanin production and hyperpigmentation risk but not necessarily sunburn.
- Combined HRT may enhance general skin sensitivity, requiring more attentive sun protection.
Best Practices for Safe Summer Sun Exposure
- Avoid sun between 10 a.m. – 4 p.m.
- Use broad-spectrum SPF 30+ sunscreen with zinc oxide or titanium dioxide.
- Apply 1 oz 15 minutes before sun exposure; reapply every 2 hours.
- Wear wide-brimmed hats, UV-blocking sunglasses, and UPF-rated clothing.
- Get 10–30 minutes of unprotected sun exposure 2–3x/week to support vitamin D.
- Add topical antioxidants like vitamin C or E to combat oxidative stress.
Product Tips
Choose sunscreens vetted by the Environmental Working Group (EWG), such as:
- C’est Moi Mineral Sunscreen SPF 45
- Badger Active Mineral SPF 30
- Biossance Squalane + Zinc
Closing Thoughts
Use sunscreen as one part of a layered sun protection strategy. Prioritize mineral options, be mindful of hormonal health, and enjoy summer safely and sustainably.
Citations:
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- Janjua NR, Mogensen B, Andersson AM, et al. Systemic absorption of the sunscreens benzophenone-3, octyl-methoxycinnamate, and 3-(4-methyl-benzylidene) camphor after whole-body topical application and reproductive hormone levels in humans. Arch Dermatol Res. 2016;308(2):75–84. doi:10.1007/s00403-015-1610-4
- Lademann J, Weigmann HJ, Schanzer S, et al. Protective clothing and sunscreens: their role in UV protection. J Am Acad Dermatol. 2018;79(3):531–537. doi:10.1016/j.jaad.2018.03.040
- Matta MK, Florian J, Zusterzeel R, et al. Systemic absorption of sunscreen active ingredients: a follow-up study under maximal use conditions. Toxicol Sci. 2021;180(1):1–10. doi:10.1093/toxsci/kfaa174
- Pierfelice TJ, Raffetto JD, Macmillan-Wei A, et al. Effects of hormone replacement therapy on skin barrier function and sensitivity in postmenopausal women. Menopause. 2017;24(9):1055–1060. doi:10.1097/GME.0000000000000885
- Pullar JM, Carr AC, Vissers MCM. The roles of vitamin C in skin health. J Invest Dermatol. 2021;141(8):1697–1703. doi:10.1016/j.jid.2021.01.029
- Rivas-Santiago B, Rivas-Santiago CE, Castañeda-Delgado JE, et al. Sunscreen ingredients and their effects on the skin barrier: a review. Dermatol Clin. 2018;36(4):369–376. doi:10.1016/j.det.2018.06.003
- Ruszkiewicz JA, Pinkas A, Ferrer B, Peres TV, Tsatsakis A, Aschner M. Neurotoxic and endocrine-disrupting potential of UV filters: a review. Environ Int. 2020;140:105779. doi:10.1016/j.envint.2020.105779
- Salih H, Psomadakis C, George SMC. Sunscreens: A narrative review. Skin Health Dis. 2024;4(6):e432. Published 2024 Aug 7. doi:10.1002/ski2.432
- Seite S, Fourtanier A, Moyal D, Young AR. Photodamage to human skin by suberythemal exposure to solar ultraviolet radiation can be attenuated by sunscreens: a review. Clin Cosmet Investig Dermatol. 2019;12:387–393. doi:10.2147/CCID.S201474