spf

SPF

SPF


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  • - NICKOO MERATI
  • - M.D.C.M CANDIDATE
  • - MCGILL UNIVERSITY

WHAT IS SPF?

WWe’ve all heard it: “UV index is high today, make sure you wear your SPF!”. But how much sunscreen do we need?
What’s the difference between SPF 30 and 50?
What does SPF mean?

SPF

SPF stands for sun protection factor and measures a sunscreen’s protection against the harmful UV radiation in sunlight.

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WHAT PART OF THE SUN DO WE NEED PROTECTING FROM?

The sun’s rays contain both visible and UV (ultraviolet) rays – UV means we can’t readily see them, but they definitely still exist and affect us. There are 3 types of UV rays: UVA rays (the kind that mostly causes tanning), UVB rays (the kind that mostly causes sunburns) and UVC (these are filtered by the ozone layer and do not reach the earth’s surface). Both kinds can cause skin cancer and premature skin aging. Broad spectrum sunscreens protect against both UVA and UVB, so broad spectrum sunscreen is best.

WHAT ABOUT THE NUMBERS?

By convention, the SPF number is calculated based on how much UVB gets blocked, because we really only knew about the harmful effects of UVB when these standards were being created. When applied in sufficient amount, SPF 15 protects against 93% of UVB, SPF 30 protects against 97%, and SPF 50 protects against 98%. SPF sunscreens < 15 are minimally effective.

SPF>50 provide a negligible increase in protection from UV radiation. The Canadian Cancer Society recommends using a sunscreen with a SPF of at least 30.

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SPF 15 or 30 or 50 – which one do I need?

Dermatologists recommend using a sunscreen that is broad spectrum, water resistant, with a minimum of SPF 30, but SPF 50+ is better. Note that water resistant is not “water proof” – you will need to re-apply right after you swim, but it helps while you swim. If you expect to spend a long day outside in the sun, you may benefit from a higher SPF just in case . Other factors may also cause you to consider a higher SPF: some common medications can make you more sensitive to sunlight such as certain antibiotics and blood pressure pills (ask your pharmacist/doctor), and some people just burn more easily at baseline (especially people with lighter skin).

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HOW MUCH SUNSCREEN DO I APPLY?

Notice I said “when applied in sufficient amount”? Well, if you don’t apply enough, those protective percentages drop. Drastically.

Many don’t wear a thick enough layer sunscreen. “In fact, on average, people apply only 20% of recommended amount of sunscreen. No wonder one bottle of sunscreen can last someone the entire summer”, explains Dr. Netchiporouk, Assistant Professor of Dermatology at McGill University. Moreover, when people sweat or go swimming sunscreen comes off easily.

Even the best sunscreens still break down and rub off after a couple of hours. So, dermatologists recommend to re-apply at LEAST every 2-3 hours. If you’re swimming, working out or actively sweating, re-apply right after. In terms of how much to apply, adults can follow the teaspoon rule: apply approximately 1 teaspoon of sunscreen to the face & neck, 2 teaspoons to the front & back torso, 1 teaspoon to each upper limb, and 2 teaspoons to each lower limb . That being said – the best advice we can give is to apply sunscreen generously.

PHYSICAL SUNSCREEN? CHEMICAL SUNSCREEN? WHAT’S THE DIFFERENCE AND WHICH IS BEST?

Sunscreen can come in two major flavors: physical blockers and chemical absorbers. They differ in their ingredients and mechanisms of action. Physical blockers use minerals as their active ingredient, such as zinc oxide or titanium dioxide, and work by reflecting the UV rays away from your skin. Chemical absorbers use organic chemicals as their active ingredient, such as oxybenzone and avobenzone, and work by absorbing the UV rays and re-radiating the energy out as heat. Physical sunscreens tend to be less irritating for sensitive skin, yet may leave a white cast to your skin on application. Chemical sunscreens tend to be easier to apply and don’t leave a white cast, yet may be more irritating for sensitive skin. Questions have also been raised about the environmental effect of chemical sunscreens potentially running off in ocean waters and bleaching coral reefs, and certain countries and islands have restricted its use. Also, recent articles showed that chemical sunscreens are absorbed into our blood stream. So, if you are concerned, you might choose a physical/inorganic sunscreen. Also, for babies, dermatologists in general recommend using physical sunscreens.

So which is the best sunscreen?

“The answer is simple”, says Dr. Ivan Litvinov, Dermatologist at McGill University. “The best sunscreen – is the sunscreen that you will use. Find the brand and type that suits your skin. That does not irritate and gives you the desired feeling and appearance. The best sunscreen for me may not be the best one for you. “

BUT MY SKIN IS NATURALLY COLORED/TANNED - I NEVER BURN, SO I DON'T NEED SUNSCREEN!

Not true! All individuals, regardless of skin type, are susceptible to the potential harmful effects of UV radiation that lead to skin cancer and skin aging. In other words, we all benefit and need sunscreen! Sunscreen is especially useful for people with lighter skin types, since light skin is more susceptible to sunburn. However, all skin types are susceptible to skin cancer. “It is estimated that ‘dark skin’ is said to have a natural SPF of 13.4 - like a natural sunscreen”, explains Dr. Litvinov, “but that is still not the minimum SPF 30 that is recommended”.

Indeed, all skin types are susceptible to skin cancer. To find out more about this important, you can visit the following page: Skin Cancer Foundation: Is There a Skin Cancer Crisis in People of Color?

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A QUICK FINAL NOTE ON SUN CARE

While sunscreen is a front-liner, many other methods should be part of your sun care arsenal! Remember that even SPF 100 does not provide 100% sun protection. Avoiding sun during peak hours (10:00AM-2:00PM) and seeking shade, wearing a hat and sunglasses, and wearing sun-protective clothing can all help reduce the potential harms associated with UV exposure. Remember that technically, there is no such thing as a healthy tan from the sun. And no tan is worth dying for (from melanoma)!