With all of the sunscreen choices out there, how does one know what to buy.  The first factor to consider is the sunscreen’s SPF number, which tells you how well the sunscreen blocks UVB radiation from the sun.  UVB rays are the rays most responsible for sunburn.  The general recommendation is at least SPF 30, which means the sunscreen allows you to stay in the sun 30 times longer without sunburn than with no sunscreen at all.  The other important factor however is protection from UVA rays, which contribute to skin photodamage, premature ageing, and skin cancer development.  The SPF does not relate to UVA rays, so it is important to get a sunscreen that has “broad spectrum” UVA and UVB protection.  Often the best sunscreens contain either zinc or titanium, which are elements that provide a physical blockage of the sun’s damaging rays, and are less likely to create an allergic reaction as compared to the chemical sunscreens.