Sunscreen, the best protector of skin

If I told you there was a cream that could prevent cancer as well as pre-mature aging, would you use it? How about if I told you could find it for $10 at any drug store?</p>

That cream is sunscreen. Somehow, sunscreen seems to be the skincare item most people are the most and the least familiar with. What is SPF? Can I use the spray instead of the lotion? How much should I apply? My moisturizer has sunscreen; do I need to add more sunscreen on top of that?

The truth is, sunscreen is the most essential skin care item there is. No other lotion, serum, oil, or cream can claim to do you more good than plain old sunscreen. Sunscreen blocks UV rays (UVA and UVB, but we’ll get to those in a minute), reduces your risk of skin cancer from sun damage, and prevents pre-mature aging caused by the sun.

First, let’s talk about UV rays. The sun naturally gives off ultra violet radiation in the form of UV rays — we can categorize these rays into UVA and UVB based on their wave length. UV rays are not visible. While the human eye can detect light from the electromagnetic spectrum from 700-400 nanometres (nm), UV rays extend from 400 nm to 290 nm. The difference between the two is essentially the wave length.

UVA can make up up to 95 per cent of the UV rays reaching Earth, according to the Skin Cancer Foundation. UVA penetrates the skin’s dermis, digging in deeper than UVB which is understood to only penetrate the epidermis. UVA rays are thought of as the cancer-causing rays, as they can damage stratum basale where keratinocytes live (basal skin care affects the basal cells in this layer). UVA can penetrate through glass. UVB rays are responsible for the tanning and redness in sunburns but not shown to penetrate glass as significantly as UVA.

To protect against UV rays, sunscreen was invented. Sunscreen can be made up of physical ingredients, chemical ingredients, or a mixture of the two. Physical sunscreens form a barrier that reflects UV rays. Titanium dioxide and zinc oxide are the main physical ingredients. While zinc oxide has been proven to protect against both UVA and UVB rays, titanium oxide is said to only protect against UVB. These ingredients also cause a “white cast” on the skin, but are effective immediately following application. 

Chemical sunscreens, on the other hand, absorb UV rays before they reach the skin. Avobenzone is a popular ingredient, along with octylcrylene, oxybenzone, and octisalate. Chemical sunscreen ingredients require a period of time to stabilize on skin before sun exposure. However, they do not leave a white cast.

Application of sunscreen is also tricky. It’s not enough to slather it on and hope for the best. Most people require a quarter of a teaspoon of sunscreen for their face for it to be effective at the SPF listed on the bottle. A study published in the British Journal of Dermatology in 2001 showed that only half the people applied this amount. One experiment done by FutureDerm on a spray sunscreen showed that it needed to be sprayed on a location for six seconds to be as effective as the lotion. 

That brings us to products that include sunscreen like foundations, bb creams, and moisturizers. To be as effective as sunscreen, you must use at least the same quantity as sunscreen — a quarter of a teaspoon, if not more. Check your instruction label to see how much you have to use for it to reach its SPF designation.

Last but not least, we have SPF. Short for sun protection factor, it is a measure of how well a sunscreen blocks UVB rays. According to Florida dermatologist James Spencer, SPF 15 blocks 94 per cent of UVB rays, while SPF 30 blocks 97 per cent and SPF 45 blocks 98 per cent. No sunscreen blocks 100 per cent of rays, and SPFs cannot be added together for additional coverage. Adding SPF 45 twice will still only give you a sun protection factor of 45, not 90. 

Most sunscreen only lasts for four hours, after which re-application is needed. 


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