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About Sun Screen
What is SPF?
The SPF 15 sunscreen allows a person to stay out in the sun 15 times longer.
SPF stands for Sun Protection Factor. The number is
determined experimentally indoors by exposing human subjects to a light
spectrum meant to mimic noontime sun.
A sunscreen with an SPF of 15 filters 92% of the UVB. Put another way, a sunscreen of 15 will delay the onset of a sunburn in a person who would otherwise burn in 10 minutes to burn in 150 minutes.
There is currently no uniform measure of UVA absorption. There are broad-spectrum sunscreens that protect against UVA and a UVB radiation although it is important to remember that the SPF does not predict UVA protection. The UV Index is a public health education tool reported by meteorologists in 58 U.S, cities. It offers a daily report of UV light levels on a scale from 1-10+.
The “protectiveness” of clothing can also be measured by SPF. The following are SPFs of various types of clothing:
- Nylon Stockings – SPF 2
- Hats - SPF
3-6
- Summer-weight clothing – SPF 6.5
- Sun-protective clothing – up to SPF 30
5 Things You Didn’t Know About Sunscreen
1. You Probably Need Another Coat – “The general rule is
a shot full for your entire body. But if you are in a bathing suit, that may
not be enough,” according to dermatologist Cheryl Karcher.
2. SPF isn’t everything – The number gauges how well a
sunscreen fends off UVB light – but not UVA rays. To ensure your sunscreen
protects against both, scan the label for the words “ broad spectrum” and more than one of the following ingredients:
avobenzone (Parsol 1789), Mexoryl, titanium dioxide, or zinc oxide.
3. Sunscreen weakens when exposed to heat and light.
Store your sunscreen in a cool place, not in the trunk of your car. Get
sunscreen with stabilizing ingredients, like Helioplex or Dermaplex.
4. You may need to wear it indoors. Unless they’ve been
specially treated, the windows of your home or office typically won’t shield
you from damaging rays, says dermatologist Francesca Fusco.
5. And underneath your clothes. The average white cotton
T-shirt provides an SPF of 10 or less.