I read on skin biology that zinc oxide and titanium dioxide are the only non carcinogen UV blockers. Parasol absorbs UV light but can't get rid of it, so it breaks down into free radicals and is only good for an hour. Zinc oxide blocks the UVA, while titanium oxide blocks the UVB and a little UVA. You do need some UV rays for optimal health and cancer prevention, though vitamin D may be the main reason. It is unknown if supplements can fix that. Anyway, a good sunscreen has zinc oxide and titanium dioxide and some anti-oxidants in it, and no other blockers in it. It may need some tinting to it, though, since those two are white.
In general it is best to have clothes that just let some UV light in, but block most, and have a hat so you get indirect light, and get about 15 minutes of direct light per day, and use sun screen if you know you will be out more than 30.
In general it is best to have clothes that just let some UV light in, but block most, and have a hat so you get indirect light, and get about 15 minutes of direct light per day, and use sun screen if you know you will be out more than 30.