When you go out into the sun you are being exposed to two types of rays:
UVA: penetrates deep into our skin but doesn’t cause sunburn. UVA rays are the same strength year round and it’s difficult to get full protection from these rays. It’s also much harder to measure since there are no visible effects from UVA rays.
UVB: are the rays that turn our skin red. They don’t penetrate as deeply but affect the top layers of skin. These are effectively blocked with sunscreen.
Both UVA and UVB rays cause damage to the skin’s collagen as well as change the DNA, which can result in skin cancer. UVB damages skin at a much slower rate than UVA.
Know Your Sunscreen
Sun protection from a bottle comes in two forms:
Sunscreens: are chemicals that absorb the radiation as it hits our skin. Broad spectrum sunscreens offer protection about both UVA and UVB although UVA protection is limited.
Sunblock: physically block both kinds of UV rays by reflecting them away from the skin. The most popular are zinc oxide (ZO) or titanium dioxide (TiO2.
Both types are called sunscreen so you have to read the labels carefully.
Sun Protection Factor (SPF) focuses on the UVB rays and never UVA – since this is impossible to accurately measure. Most of us have been using the SPF factor incorrectly.
The classic formula of taking the SPF and multiplying by ten to give you how many minutes of protection doesn’t work. That’s because according to the FDA, SPF actually measures the amount to sun exposure and not the protection time. It’s impossible to accurately measure how many minutes of protection is being offered since there are so many variables including the strength of the sun, time of day and a person’s skin.
Use SPF to determine how much UVB is blocked:
- 2 SPF blocks 50 percent
- 10 SPF blocks 90 percent
- 15 SPF blocks 93 percent
- 30 SPF blocks 96.67 percent
- 50 SPF blocks 98 percent