Chemical ingredient formulations (most commonly used by sunscreen makers are: avobenzone, oxybenzone, benzophenone, octyl methoxycinnamate, octyl salicylate, para-aminobenzoic acid (PABA), methyl salicylate, padimate A, Padimate O, and homosalate) must be applied 30 minutes prior to going outside because that is how long it takes for those ingredients to become effective.
Don’t be fooled by “waterproof” and “water resistant” – there is NO SUCH THING.
ALL sunscreens must be reapplied every 90-120 minutes while outside or immediately after swimming or intense sweating to keep their efficacy. SPF 15 is said to be enoughfor daily wear for the average person. SPF 30-50 is recommended for people with sun-related medical problems. Or, for those who spend longer hours or days in the sun.
Spray cans are not effective in providing a thorough, precise application as a regular tube of sunsccreen. Spray cans provide an uneven application therefore increasing the likeliness of burning.