you should use a minimum spf a 15 but even more importantly than that you can even go higher to a 30 or up to a 50. i think beyond that it doesn't make much difference. but the most important thing is to reapply it every few hours because whether or not you are out there swimming sweating or rubbing it off it wears off over time and it gets degraded by the sun exposure itself. so you have to apply enough product but also reapply it often enough in order to maintain that protection. don't forget to put it on your neck and your chest because those are areas that are exposed. if you are wearing a scoop neck or a v-neck and you are just walking around it's incidental sun exposure. the sun exposure is cumulative. your skin remembers that first exposure as a child and that's been building up building up building up in your skin and eventually it crosses a threshold when you hit your; it could be in your 20s 30s 40s or beyond depending on your skin type and how much exposure you have had where all of a sudden it starts to show. both as signs of aging and even worse signs of skin cancer.
what level of spf should one use on a daily basis?