Question:
I've recently started running and then started worrying about sun
exposure after I got a mild burn my nose. I typically don't burn
easily, I was running for around 2 hours before I burned my nose. I
didn't even notice it until I showered that night. It stung a little
bit, but not much more.
I use SPF 30 Coppertone Sport Gel, and I haven't really had any
problems with it. It's prevented me from burning anyway. I know
higher SPF is better, but is there a point of "diminishing returns"
where higher SPF doesn't make too much difference? Does waterproof
mean the same thing as sweatproof? I saw a bottle of SPF 50 sunblock
that says waterproof, but not sweatproof at the store. Are there
certain active ingredients that I should look for? I noticed that
different sunblocks have different ingredients.
Does sunblock completely prevent all UVA and UVB from penetrating?
Will that cause problems with the synthesis of Vitamin D which is
necessary for calcium absorbtion? I'm thinking of using sunblock daily
to potentially lessen my chances of skin cancer, that's why I ask.
Answer:
I'd think that waterproof means that it won't wash off if the water
comes from the outside of your body, ie, going into a pool. It may
wash off if the water comes from underneath it as happens when you
sweat. You probably should go with sweatproof.
If they are advertised then they *should*. I don't know of a way of
telling other than a scientific study.
I'd guess that a combination of all energy sources from
sunlight combine to give the energy to make vitamin D. You may not
produce as much if you block UVA and UVB. But you should perhaps
produce some amount. Doctors or knowledgable people out there please
fill in details.
