In The Know Science

SPF – do the numbers count?

Summer in the Northern Hemisphere is here!!! The continuing health crisis has more people than ever flocking to the outdoors for exercise and socializing, seeking solace in the fresh air. During this time of year, the sun rays are the strongest and most damaging and you need daily sun protection. Whether you’re shopping online or donning your mask for a trip to the pharmacy, you’ll find an overwhelming amount of choices. What do the SPF numbers mean, and how do you know which protection is best? The Hot Girls are here to help!

Sunlight contains three types of ultraviolet rays: UVA, UVB & UVC. The atmosphere and ozone layer absorb 100% of UVC rays, about 95% of UVB and 5% UVA. Of the rays that reach the Earth’s surface, UVB rays affect the outermost layers of skin, causing sunburn and the most significant risk of developing skin cancers. UVA rays penetrate our skin deeper and are responsible for changes in pigmentation, skin aging and can cause damage to our immune systems and DNA.

SPF stands for “sun protection factor” and measures the fraction of how much longer a sunburn takes to develop on protected skin. SPF 15 blocks 93% of UVB rays, and 1/15 of the radiation will reach your skin, meaning it would take 15 times longer to get a sunburn than it would with no protection. SPF 30 provides most of the coverage, blocking 97% of UVB radiation and doubling UVB radiation exposure. 50 provides an additional 1%, and the percentages marginally increase as the SPF gets higher. It’s important to note that no sunscreen protects 100% of the sun’s UV rays. 

We tested out four Neutrogena sunscreens, each with different SPF. This is after two hours of direct sun exposure. Can you tell which has the highest SPF?

Here is the breakdown:

Square 1 – SPF 55 Square 2 – SPF 30 Square 3 – SPF 70 Square 4 – SPF 110

We personally were shocked to see that it was rather hard to tell the difference between the four. The truth is, while a higher SPF can offer the most protection, it can also mislead people into thinking they’re more protected than they are, often leading to its misuse. There’s also concern that most sunscreens only protect against UVB rays, leading to overexposure to harmful UVA rays. Only products labeled “broad spectrum” protect against both; however, it’s challenging to find the right balance in protecting both in higher SPF sunscreens.

So which number SPF is best? Hot Girls Know that’s a personal choice. Remember – regardless of what number you choose, make sure you’re getting total UV protection by selecting a sunscreen that’s broad spectrum, putting on the correct amount before sun exposure, plus reapplying every two hours and after toweling off water or sweat. 

Hot for more?

READ: Sunscreens and Photoprotection

LISTEN: Skincare Secrets: #7 The 3 most important things to know about SPF

WATCH: SPF explained by the inventor of the UV Index

Featured photo by Maciej Serafinowicz from Unsplash

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