1. Sunlight has UVA and UVB rays ,both of  which affect skin in different ways.
  2. UVA rays basically cause skin tanning and UVB rays cause skin burns and redness.
  3. Most of us keep SPF as a guideline for choosing a sunscreen,assuming that, higher the SPF better the sun protection, which is absolutely incorrect.
  4. When we choose sunscreen we need to know what type of skin one has so that a ideal sunscreen can be chosen.
  5. Depending on reaction to sunlight , universally skin is categorized into six types.
  6. Most of the INDIAN skin is category 3-5 which is more prone for tanning than skin burns and higher SPF sunscreen cannot prevent tanning. Most of INDIAN skin don't need a SPF more than 20.
  7. In simple terms SPF is not a measure of tan protection, its in fact a measure of skin burn protection.
  8. There is one more factor called PA value on sunscreen, which is a measure of Tan protection.
  9. Sunscreens don't last for more than 3-4 hours, so one needs to reapply to get complete benefit . 
  10. If you want to choose ideal sunscreen for your skin, you should consult a dermatologist once who can prescribe one which suites  your skin and will not cause commonly seen side effect with wrong sunscreens like acne, dull skin, oily look,etc