This is a frequently asked question.
FDA has recommended that sun protection products be referred to as sunscreen, instead of sunblock.
In theory, a sunblock can offer up to 97% UV protection. In practice, this is rarely achieved.
Because, there are simply too many variables to the equation.
Firstly, SPF refers to protection against UVB. The higher the SPF, the longer the time that one can spend under the sun without getting becoming toast. SPF does not encompass UVA protection.
Secondly, protection from sunscreen decreases over time. Some gets removed with sweat, water or blotting tissue. Ingredients degrade under the sun, losing protective function.
Should I pick an SPF that is as high as possible?
The higher the SPF, the denser will be the product, and would feel thicker when applied on the skin.
SPF selection should be based on the level of activity or sun exposure anticipated. SPF 15 for basic protection, SPF 30 if more time spent outdoors, SPF 50 or more if skin is particularly sun-sensitive, or if receiving treatment for pigmentation.
What is the maximum UVA protection to look out?
PA is one of the standard of measure of UVA protection. Other indices are IPD (immediate pigment darkening), PPD (persistent pigment darkening), UVA seal or star rating systems.
Although FDA has approved a new rating system to measure UVA protection, this will not be enforced till 2011.
For now, the only safeguard is to look at the ingredients carefully. Only ingredients such as Titanium Dioxide, Avobenzone, Meroxyl SX, Zinc Oxide can give the best protection against UVA.
