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What is SPF? An Overview about Sun Protection

Updated: Aug 28, 2023

Executive Summary: This post breaks down what SPF is, why it’s important, and answers your most frequently asked questions about sun protection. Sparknotes version: Wear SPF every day, no matter who you are or where you’re going!

How many times in your life have you been told, “make sure you wear sunscreen”? Maybe you hear it so often, you automatically put on sunscreen before walking out the door. Maybe you’ve never thought about SPF protection, or no one has ever told you it’s important for you. Maybe you've heard about how important sunscreen is, but you might not know exactly why.

Well, don’t worry, because all your (sun)burning questions will soon be answered! This post will go over the following:

What is SPF?

Sun protection factor (SPF) is a number found on products such as sunscreen or skincare to indicate the degree of protection it provides your skin against UV radiation (1,2). The higher the SPF level, the greater protection to your skin it provides, for a longer amount of time. For example (3):

  • SPF 15 blocks 93% UVB rays and it would take approximately 15x longer to burn than if you weren’t wearing SPF

  • SPF 30 blocks 97% UVB rays and it would take approximately 30x longer to burn than if you weren’t wearing SPF

  • SPF 50 blocks 98% UVB rays and it would take approximately 50x longer to burn than if you weren’t wearing SPF

Why do we need protection from UV radiation?

UV radiation, also known as ultraviolet radiation or UV rays, are energy wavelengths from the sun. UV radiation also comes from artificial sources such as tanning beds and black lights (4). UV rays are invisible to the eye but are felt and absorbed by our skin. For instance, if you’ve ever sat in direct sunlight for any length of time and you felt your skin tingling, that is an example of how we can feel, but not see, our skin’s reaction to UV radiation.

There are two types of UV radiation wavelengths that impact our skin health: UVA and UVB rays (4). SPF sunscreen protects us from both (5; 6):

  • UVA. Causes immediate tanning of the skin, premature skin aging (e.g. wrinkles, leathery skin), and may contribute to the development of skin cancers.

  • UVB. While approximately 95% of the sun’s UVB rays are absorbed by the ozone layer, it is the deadliest form of UV radiation. Exposure to UVB is responsible for sunburns and most skin cancers.

Wearing SPF prevents these harmful rays from impacting our long-term health. Every time you expose yourself to UV radiation without SPF, you damage your skin. Skin damage, such as tanning and sunburning, increases the risk of skin cancer. Therefore, it is important to wear SPF all the time so you can prevent the development of skin cancers (listed from most to least common in Canada) (6; 7*):

In what is currently known as Canada, statistics on non-melanoma skin cancers are not collected, however, approximately 1,300 people die from melanoma each year (7*; 8). Melanoma, and all types of skin cancers, can largely be prevented by wearing SPF! Yay!

Frequently Asked Questions on SPF

1. Do I need SPF in the winter, when it’s raining, or if I’m inside all day?

We do need SPF no matter where we live or what season we’re in. Both UVA and UVB rays are present during colder, cloudier days even in the winter. Even if we don’t feel the sun rays like we do in direct exposure during the summer, they’re still there. While UVB rays are lessened by clouds, fog, and rain, UVA rays are not and they can reach our skin even through glass (9). Even if you know you’re going to be inside all day, wear sunscreen.

2. Do I need to wear sunscreen if I am a person of colour?

Yes! The misperception that people of colour do not need to wear sunscreen comes from the idea that SPF is only meant to stop people from getting a sunburn, and people of colour ‘don’t get sunburnt’ (10). First, anyone can get sunburnt regardless of skin tone or skin colour. Second, while SPF protects folks from sunburns, its real purpose is meant to protect our skin from absorbing harmful UV rays, regardless of if we get sunburnt or not. People of colour can still damage their skin from UV ray exposure, though the damage may manifest as premature aging or sun spots rather than a sunburn. It is important for everyone to wear SPF to protect ourselves against skin damage and subsequently, skin cancer. This misperception is dangerous, as it leads to skin cancer often being diagnosed at a later stage for BIPOC folks, which ultimately reduces the chances of survival (11; 12).

Note: Dark-skinned folks are less likely to get sunburnt, due to dark skin’s natural production of melanin. Melanin acts as a natural SPF and does protect the skin from harmful UV rays on a small scale. However, it is recommended by dermatologists for dark-skinned folks to still wear a minimum of SPF 30, as UV rays can still penetrate the skin and cause skin cancer (10; 13).

3. Can I still tan and wear SPF?

You can tan while wearing sunscreen with any level of SPF. The real question here: is it safe to tan? The answer is no. Tanning = damaging skin, regardless of whether you’re tanning in the sun, a tanning bed, or sun lamps. When you are tanning, your skin increases its production of melanin which creates a darker skin tone (14). This process can lead to DNA mutations which can lead to the development of skin cancer. So, if you want to tan safely, use self-tanner (bonus if it has built-in SPF)!

Note: It is not recommended to use tanning oils, even if they have SPF. Tanning oil amplifies the intensity of the UV rays, which speeds up your tan... and increases your risk of skin cancer. Any tanning product that claims to help you achieve a ‘safe tan’ is inaccurate (15; 16).

4. What level of SPF should I wear, and how much do I use?

You can use non-sunscreen products with SPF (e.g. moisturizers, lip balm, self-tanner, lotions, etc.), however, they often have low amounts of SPF (less than 15). Therefore, it is recommended to wear sunscreen in addition to SPF products you may use. The American Academy of Dermatology recommends wearing an SPF sunscreen of 30 or higher, broad-spectrum (meaning it protects you from both UVA and UVB rays), and water-resistant for optimal skin protection (17).

Rule of thumb: Applying a shot glass amount (just 1 ounce) of sunscreen to your entire body is enough to protect you from harmful UV rays. Use more sunscreen if you need more to cover all of your body. The key is to keep reapplying sunscreen every 2 hours, as it can wear off quickly through sweating, swimming, or by rubbing on your clothes (18). The more you reapply, the better protected you will be!

5. Should I use a spray or lotion sunscreen?

Both types of sunscreen are safe and effective forms of SPF. However, using a spray sunscreen can result in applying too little sunscreen, and therefore reducing your SPF protection (17).

6. If I layer a SPF 15 product with a SPF 30 product, am I wearing an SPF of 45 now?

No. The level of SPF does not accumulate if you layer multiple products with varying levels of SPF. The highest protection you have is based on the highest SPF product you put on. In this case, you would have an SPF of 30. However, some products have lower amounts of SPF than advertised (often the case with makeup products), therefore layering with sunscreen will significantly improve your sun protection (18).

Thank you for taking the time to learn about the importance of wearing SPF. I don’t know about you, but I really feel like I need to put on sunscreen!

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8. Canadian Cancer Society. Non-melanoma skin cancer [Online]. Canadian Cancer Society; n.d. [cited 31 May 2021]. Available from:

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11. Skin Cancer Foundation. Ask the Expert: Is there a skin cancer crisis in people of colour? [Online]. Skin Cancer Foundation; 2020 Jul 5 [cited 31 May 2021]. Available from:

12. Cleveland clinic. What dark-skinned people need to know about skin cancer [Online]. Cleveland Clinic; 2019 May 9 [cited 31 May 2021]. Available from:

13. Diffey BL, Fajuyigbe D, Wright CY. Sunburn and sun protection in black skin. Int J Dermatol. 2019;58(9);1053-1055.

14. U.S. Food & Drug Administration. The risks of tanning [Online]. U.S Food & Drug Administration; 2019 Apr 26 [cited 31 May 2021]. Available from:

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16. The International Agency for Research on Cancer Working Group on artificial ultraviolet (UV) light and skin cancer. The association of use of sunbeds with cutaneous malignant melanoma and other skin cancers: A systematic review. Int J Cancer: 2006 March 1;120:1116–1122.

17. American Academy of Dermatology Association. Sunscreen FAQs [Online]. American Academy of Dermatology Association; n.d [cited 31 May 2021]. Available from:

18. American Academy of Dermatology Association. How to apply sunscreen [Online]. American Academy of Dermatology Association; n.d [cited 31 May 2021]. Available from:

19. Kim MA, Jung YC, Bae J, Ha J, Kim E. Layering sunscreen with facial makeup enhances its sun protection factor under real-use conditions. Skin Res Technol. 2021 Mar 3;00:1-7.

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