Understanding SPF (Sun Protection Factor)

If you are into cosmetics, and you do not know the meaning of SPF; I think you are doing your customers more harm than good. Which is why I will be talking about it in today’s post.

What is SPF Sunscreen?

SPF, stands for Sun Protection Factor, it is a measure of how well a sunscreen will protect your skin from the UVB rays; the kind of radiation that causes sunburn, damages the skin, and can contribute to skin cancer.

Ultraviolet light is invisible to human sight because it has shorter wavelengths than the light we can see. Within the UV spectrum, there are two types of rays that can damage the DNA in your skin cells and lead to skin cancer. So, it’s important to protect your skin from both types of rays:

UVB (ultraviolet B) rays – It is a light from the sun that has a fairly short wavelength and causes the skin to go brown and look older. It causes sunburn and plays a key role in developing skin cancer. A sunscreen’s SPF number refers mainly to the amount of UVB protection it provides.

UVA (ultraviolet A) rays – It is a light from the sun that has a fairly long wavelength and causes the skin to go brown and look older. It causes skin damage that leads to tanning as well as skin aging and wrinkles.

If your skin would normally burn after 10 minutes in the sun, applying an SPF 15 sunscreen would allow your skin to stay in the sun without burning for approximately 150 minutes (a factor of 15 times longer). This is a rough estimate that depends on skin type, the intensity of sunlight and the amount of sunscreen used. SPF is actually a measure of protection from the amount of UVB exposure.

SPF 15 blocks 93% of UVB rays

SPF 30 blocks 97% of UVB rays

SPF 50 blocks 98% of UVB rays

So, one way of looking at this is that SPF 30 sunscreen only gives you 4% more protection than SPF 15 sunscreen.

Or, another way of looking at it is:

SPF 15 (93% protection) allows 7 out of 100 photons through

SPF 30 (97% protection) allows 3 out of 100 photons through.

So, while you may not be doubling your level of protection, an SPF 30 will block half the radiation that an SPF 15 would let through to your skin.

As mentioned above, SPFs generally only offer protection against UVB rays which are the rays that cause your skin to burn, meaning that you are still exposed to sun damage from UVA rays.

An SPF 50 will give you 50x the sun protection of what your skin naturally provides so a smaller amount of damaging UVB rays are able to penetrate and damage your skin than lower SPFs. It is important to remember to apply your SPF 50 as often as you would a lower SPF though to ensure your skin is continuously protected throughout the day. Don’t take that extra protection for granted!

Most dermatologists recommend using an SPF between 30 and 50.

Going higher than SPF 50 can be counter-productive as people are misled into a false sense of security. Above SPF 50, the increase in protection is minimal and people are encouraged to neglect other protective habits such as seeking shade and wearing sun-protective clothing, so even if they don’t burn they can still get sun damage from UVA rays.

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