The 2 ray-UVA rays(aging rays) responsible for long term skin damage because they absorb deep into skin.
-UVB rays cause skin tan or sunburn.
What is SPF?
Sun Protection Factor(SPF) label range from 2 to as high as 100 and refer to product's ability to screen or block out the sun harmful rays. This is a sun metre and often products inadvertently allow tanning with enough sun exposure.
Sun's protection factor is calculated this way:-Take the time u would normally burn in the sun without protection. 20 minutes will usually produce redness on light skinned individual.
-Multiply the number by the SPF of ur product. Example with an SPF 1x 20 minutes of sun time = 300. This is how many minutes u can stay in the sun without burning. 300 minutes(5 hours) of sun protection without a sunburn.
U need to aware that SPF protection does not increase proportionally with an increased of SPF number. SPF greater than 15 offer only small increment of additional protection.
Which SPF is right for me?
For most people, sun protection of SPF 15 provide adequate protection as long as evenly applied and frequently reapplied. People who are fair-skinned, light-coloured, sensitive skin will benefit from a higher SPF. Does highest mean best protection? Not necessary. An SPF of 50 only provide 1% or 2% more protection than SPF of 30.
Waterproof vs Water Resistant
If u are looking for a a sunscreen to use while in water, choose sunscreen that is "water resistant" or "waterproof"? "Waterproof" sunscreen provide protection in the water for 80 minutes, while "water resistant" provide only 40 minutes of protection.
