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Get All the Facts about
Sun Protection Factor



What is Sun Protection Factor or SPF Number?

All sunscreens have a sun protection factor or SPF number displayed on the labels. It refers to a product's ability to shield or block out the sun's harmful UVB rays. Hence the higher the number of the SPF the greater the sun protection.

The SPF rating represents the length of time that a sunscreen-protected skin can be exposed to UVB rays before a minimal redness(erythema) appears, compared to the length of time it takes on unprotected skin.

In other words, it indicates how much longer you can be exposed to the sun before getting sunburn. For example, if you use a sunscreen with a SPF 15, you can be in the sun 15 times longer that you can without sunscreen before burning.

The amount of time it takes for unprotected skin to burn depends on skin type. In general fair skin burns more quickly than darker skin.

For example, if without using a sunscreen it normally takes Alice 14 minutes of sun exposure for her skin to get a sunburn, then with SPF 15 sunscreen would ideally provide (14 x 15 =210) 210 minutes of protection for Alice.

But normally protection is less because sunscreen gets washed off by sweat and also get wiped off. In practical use, sunscreen need to be reapplied every 2 hours



How Much Protection do You Get?

It is also important to note that SPF protection does not actually increase proportionately with a certain SPF number. For example,

  • SPF 2 will absorb 50% of the UV radiation

  • SPF 4 absorb 75%

  • SPF 15 absorb 93%

  • SPF 30 absorb 97%

But SPF number on sunscreens only reflects the screening ability for UVB radiation, it is important to select a broad-spectrum sunscreen that also protects you from UVA radiation. At present there is no rating system that measures the degree of protection from UVA exposure.

A few sunscreen labels also list a "PA" ranking, which refers to the amount of protection the sunscreen offers from the UVA rays that may cause long-term skin damage. PA rankings are listed as PA+, PA++ or PA+++. The more +'s, the more protection from UVA radiation.

Approximately 35ml of sunscreen must be applied to the total body surface of an adult to result in a sun protection factor quoted on the label. Clothing provides the ideal barrier from the sun and more economical in the longer run. The type of clothing can make a big difference in sun protection factor. How to select sun protective clothing.



Take a QUIZ! If I am using sunscreen, I can stay in the sun as long as I want. TRUE or FALSE?

The answer is FALSE. It is not smart to broil yourself in the sun for several hours, even if you are using sunscreen. These products do not provide total protection from ultraviolet rays. The American Cancer Society recommends that we seek shade and limit exposure to the sun during mid-day. Also cover up with a proper shirt, wear wide-brimmed hat and sunglasses



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