Posted on Apr 25, 2012 in Health & safety, Science & nature
How does sunscreen work? It’s like magic, right? You smear some (usually) nice-smelling lotion all over your skin and you magically don’t get a sunburn. How does sunscreen actually work?
Not just the subject of an oddly popular 1999 hit by Baz Luhrmann, it’s that stuff we slather all over ourselves to keep from becoming reddened, blistered, crying messes after a day at the beach.
Okay, so we know sunscreen works. The question is… how?
Before we can talk about how sunscreen works its magic, we have to take a minute to discuss what it is trying to prevent — sunburn.
A sunburn is exactly what it sounds like — skin burned by the sun. Overexposure to ultraviolet (UV) radiation from the sun (or other UV source — welding without a mask can give you a nasty burn) causes the skin to turn reddish, possibly blistering in extreme cases, and general fatigue and even dizziness. Since it’s the UV and not direct sunlight that causes the burns, yes: it’s still possible to get a sunburn on a cloudy day.
Excessive unprotected exposure to UV radiation has been directly linked to skin cancer, as well as macular degeneration and cataracts in the eyes. Good sunglasses are the protection for the latter two, obviously, with sunscreen and you know — clothing — being the protection for the skin.
There are two basic types of active ingredients used in sunscreen — organic and inorganic.
Inorganic sunscreens include compounds such as titanium dioxide and zinc oxide, which work by scattering and reflecting the UV radiation to lessen the exposure.
Organic ingredients include such tongue-twisters as octyl methoxycinnamate, 4-methylbenzylidene camphor, avobenzone, oxybenzone, and homosalate. Try saying those five times fast. Anyway, the organic sunscreens work by absorbing the UV radiation and dissipating it as heat energy. Most sunscreens on the market use a combination of organic and inorganic ingredients for maximum effectiveness.
Sunscreens, as I’m sure you’ve noticed, are rated by SPF — or Sun Protection Factor. There’s actually a big fancy formula the sunscreen manufacturers use to calculate SPF and trust me, you don’t want me to go into here. An SPF 15 sunscreen doesn’t mean you can go 15 hours in the sun without getting burned, it doesn’t really mean you get 15x the protection of no sunscreen at all. It just means the higher the number, the more protection it offers.
So why don’t they just offer one sunscreen at the highest SPF possible?
Well, marketing, for one — more products to offer means more money. However, some people want to keep from getting burned while still getting a tan, and, of course, some people (typically those with fairer skin) are much more susceptible to burning than others.
Mrs FF, for example, will turn red just walking out to get the mail in the summer, whereas I can wear SPF 30 and stand in the desert sun all day and just get a nice tan out of it.
Photo by inhisgrace
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