1. What does SPF stand for?
Sun Protection Factor: A rating determined by the percentage of ultraviolet B rays (the kind that lead to sunburn) that the product blocks, and the amount of time it fends off a burn.
2. Every 2 hours
The rate at which you should reapply sunscreen. Do it more often if you are sweating a lot.
3. Broad spectrum
Blocks both UVB and UVA rays (the latter cause skin cancer and premature ageing). Products that don’t block UVA, and ones with SPF below 15, must state they only prevent sunburn.
4. Higher SPF ratings (50+)
The SPF rating above which researchers have found little evidence of better protection. In the future, it may be the highest number allowed to be printed on product labels.
5. Slather guide
To cover:
- Face, head and neck: Use one tablespoon
- Both arms: Two tablespoons
- Torso (front and back): Four tablespoons
- Both legs (more if you don’t shave): Four tablespoons
The place more cyclists forget to put sunscreen? The neck (the back of it in particular)
Number of minutes dermatologists recommend letting sunscreen dry before you head outside: 20
Source: http://www.health24.com/SkinCare/all-you-need-to-know-about-sunscreen-20171011