“SPF,” better known as “sun protection factor” is the ability of a sunscreen product to delay sun redness or the sign of sun damage when applied to the skin. The SPF in the product is protecting your skin from UVA and UVB light produced by the sun rays. UVA light penetrates deep into the skin; into the dermis, damaging collagen and elastin. UVB light is the sunrays that cause a not so pretty and often uncomfortable burning of the skin.
Most sunscreens SPF refer to the amount of UVB protection. An SPF 15 blocks 93% of the UVB radiation. An SPF of 30 blocks 97% and wearing SPF of 50 blocks 98% of the sun’s UVB rays. As you can see the amount of protection from 30 to 50 is minimal.
UVA protection is even more important. The UVA rays are considered the “aging rays.” When purchasing a sunscreen, the higher SPF may protect from burning, but it is not protecting you against aging. You want to make sure your sunscreen has both UVA and UVB protection. A sunscreen with an SPF of 30 works well. I would suggest nothing lower than an SPF 30. If you must go higher, because that 1% makes a difference to you, then 50 is also fine.
Remember, the main ingredients you’re looking for in a UVA/UVB sunscreen are zinc oxide, titanium oxide.