Teach Soap

Levels of SPF above 30 make very little difference, except to your pocketbook.

The 60 and 120 cost the exact same as the 30.

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~~Heather~~
Mad [soaping] Scientist

If they're the same price these days, then get the higher SPF. It will add 1-3% to the effectiveness. 30 SPF blocks out 97%.

I thought the SPF had to do with how long you were protected in the sun based on your own skin? Ie SPF 15 let's you stay out X times longer than unprotected. Which would mean you'd likely have to reapply more often.

Sunblock only lasts a period of time, no matter the SPF. That's one of the problems with people using high SPF sunblocks, they think they don't need to reapply them - and they burn.

No matter the SPF, you must reapply sunblock after the recommended time or particularly after swimming. Just because an SPF of 15 means you absorb 15x less UVB in theory, it doesn't mean you can stay out in the sun 15x as long. Note - sunblock doesn't protect you from UVA rays, which are considered more damaging than UVB rays.

If you're using the same brand of sunblock, be it 15 SPF, or 30 SPF, or 100 SPF, you need to reapply all of them at the same time - the time the manufacturer has determined for effectiveness. They'll change the % of UVB rays you absorb during that time, but they won't let you stay out longer.

My dermatologist recommends using SPF 30, which blocks 97% of the sun's UVB for whatever period the sunblock says it will last.

I found an article last night that explained it well. No, I didn't think SPF 15 meant 15x as long, but I thought there was a formula out there somewhere. I saw the 97% of SPF 30 and then something, maybe 50 was about 99%, but same as you said, it said anything over that isn't doing any good. Even the 15 was in the high 90's IIRC. Broad spectrum seems to be key.

Years ago before I discovered I had an allergy to MTBE (a gasoline additive), I remember looking for something titanium based. It must've blocked another set of rays, but it didn't help the problem I had

My Dad is a dermatologist, he only recommends the 100+ SPF for those of us who rival bleached white sheets in skin tone LOL. Otherwise he recommends the SPF 50 broad spectrum from Ombrelle (fewer people have allergy issues with that brand), he does not recommend trying to make one though!

_________________
~~Heather~~
Mad [soaping] Scientist