Ask a Dermatologist: Dr. Shereene Idriss on All Things SPF

SPF number matters…a lot! On average, SPF 15 offers 94% protection whereas SPF 50 offers 98%. At 94% protection, your skin is still exposed to 6% of UV rays, whereas at 98% protection, only 2% of those rays make it through. That’s nearly a 70% increase in protection! So although a 4% increase in SPF may not seem significant at first, it is in fact a huge amount.

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Everything You Need to Know About Homosalate, Sunscreen’s Hero Ingredient

UVB-blocker: Homosalate, in particular, is a UVB-blocker, protecting against the UV damage that is known to cause skin cancer, says Fincher. To that point, “since it has very limited efficacy against UVA rays, it needs to be combined with other agents to ensure complete protection,” adds Idriss. (She also notes that homosalate isn’t particularly photostable and needs to be combined with other ingredients to keep it stable as well.)

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Is Sunscreen Bad for You?

Dermatologist Dr. Shereene Idriss says, “This study is not meant to scare anyone or modify behaviors. This study is shedding light on a topic that requires more studies and more data in order to reach an objective, clearly defined conclusion. The sun’s UV rays are a known, well-established, scientifically proven cause of skin cancer.”

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