Let’s be clear on SPF…

Let’s be clear on SPF…

In today’s post, we would like to clear the water around SPF and the levels of protection you use on your skin.
Here are three SPF facts you might not be aware of but must know:
1. SPF measures the level of protection from only UVB waves- the rays that make the skin burn and contributes to skin cancer.

2. SPF does not include the levels of UVA protection that also damage skin.

3. Most dermatologist advice we use sunscreens with SPF of 15 or 30 as higher SPF does not guarantee higher protection.

SPF or Sunburn Protection Factor is a measure of how well a sunscreen will protects us from UVB rays- the kind of rays which cause sunburn, damage our skin and contribute to skin cancer.

  • If your skin would normally burn after 10 minutes of sun exposure, applying a sunscreen with SPF 15 would allow you to stay under the sun without getting sunburn for approximately 150 minutes. What SPF does is prolong the usual amount of time you sunbathe before getting a sunburn. However, these numbers are a rough estimation as it all depends upon the skin type, the intensity of the sunlight, and the amount of sunscreen you are using.
  • For best protection, experts recommend using a sunscreen with no less than SPF 15 applied on your skin in the proper amount- about 2mg/cm2 of skin, or about one ounce for full body coverage. Reapplying is required at least every two hours, more often if you are sweating too much. Even if you buy a waterproof sunscreen would be best if you reapply it on your body after being in the water.
  • What most people do is apply less than the amount of sunscreen their skin needs in order to stay safe (about ¼ to ½ the amount required). However, what most of us are not aware of is that when you apply half of the amount of sunscreen lotion your skin requires this provides you with the square root of the SPF. So if half application of SPF 30 sunscreen is applied on your skin, you will get only an SPF of 5.5 to protect you effectively.

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Why do we not need to use the highest level of sunscreen protection?

Sunscreens with SPFs of 50, 75 or 100, do not offer better protection than a sunscreen with SPF 15 or 30. People are often misled into thinking that when applying a lotion with higher SPF, their skin is more protected. Most often, higher SPF sunscreens offer far greater UVB than UVA protection which gives people a false sense of full protection. In order to protect your skin to the highest level, you must pay attention to the labels and choose sunscreens with UVA protection at least 1/3 the amount of the UVB protection.

Here is our SPF scale which could make things clear in percentages:

  • SPF 15 blocks 93% of UVB rays
  • SPF 30 blocks 97% of UVB rays
  • SPF 50 blocks 98% of UVB rays

Another way of looking at this is that a sunscreen with SPF 30 gives you just 4% more protection than a sunscreen with SPF 15.

  • SPF 15 (93% protection) allows 7 out of 100 photons through
  • SPF 30 (97% protection) allows 3 out of 100 photons through


The most important thing to remember when choosing and buying the sunscreen for your next holiday is to check the label and look for medium level of SPF (15-45) with a protection from UVB as well as UVA rays.