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Dear scientists,
I have another question: many sun screens rant and rave how they are sweat resistant and waterproof. What chemicals make this function possible?
Question Date: 2009-05-18
Answer 1:

Usually an ingredient is add that is hydrophobic (repels water) such as oil,vaseline or dimethicone. That is why the directions say to re-apply after a specific amount of time since the sunscreen can be rubbed off.

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