So what’s with all the hype about sunscreen anyway?

Science has proven that skin cancers including both non melanoma and melanoma skin cancers are affecting more and more people world-wide. We also have increasing evidence that these cancers are related to UV exposure. Further, we know that cosmetic changes on the skin such as wrinkles, laxity, solar lentigines, and other pigmentary concerns are all related to cumulative UV exposure. In fact, there are cool photos around of people such as long distance truck drivers, who have had chronic sun exposure through the driver side window, resulting in dramatically more photoaging effects seen on the left side of the face as a result of all of that UVA that comes through the car windows.

For all of those reasons, protecting your skin from chronic sun damage is extremely important. As a dermatologist, I am a passionate advocate on this subject. Protecting skin from these damaging effects makes up as much as 70% of what I do.

So how do we protect our skin?

Well of course there are the not fun things, like staying indoors or not going in the sun. But myself and my family are full on outdoor enthusiasts. There is nowhere that I would rather be than sitting next to the lake listening to the waves, or speeding down a deserted highway on my road bike.

So we go outdoors and we enjoy the many benefits nature, fresh air and exercise have to offer, all the while staying sun safe.

Sun safety includes sun umbrellas, sun hats and UPF protective sun clothing, seeking shade and using sunscreen.

Some studies show that wearing sunscreen provides persons with more reckless sun behaviors, giving them a false sense of security that you can stay outdoors all day in direct sun.

Remember, you will, still get UV light through to your skin even when wearing sun screen, it is possible to tan and even burn even with sunscreen on.
Remember to use sunscreen in combo with seeking other forms of sun protection.

Remember that common protective ingredients in chemical sunscreens will break down in the sun with time, so they need to be reapplied every two hours, after exercising or sweating, or after swimming.

Even physical blocking sunscreens that contain Zinc oxide and titanium dioxide need to be reapplied as they are thought to move around on the skin and clump into the creases with movement and water exposure.
The sunscreen market can feel a little overwhelming but hopefully I can try to clarify some points for you here today.

What are sunscreens even protecting us from anyways?

Now time for a little science without making you want to cry (hopefully).

Well Ultraviolet light makes it down to the earth via the sun’s rays.
Within that ultraviolet light there is UVC, UVB, and UVA.

Sunscreens are meant to reduce the effect of UV light and the targeted interaction in the skin to generate photochemical reactions that lead to photo biological change.

Early sunscreen ingredients blocked UVB which is thought to be mostly responsible for burning and the development of skin cancers.

And newer ingredients combine with UVB filters to block the longer wavelength UV radiation known as UVA, which we believe to be responsible for Photoaging changes in addition to its contributions to skin cancers.

Because these days I spend a lot of time doing learning activities with a 3 and a 5 year old and we do a lot of things like A is for Aardvark and B is for Blizzard….
You can think of it like UVAge and UVBurn

The efficacy of sunscreens is based on what is known as the SPF, or the sun protection factor.
The SPF is determined by skin phototesting using artificial light in a lab.

Essentially, scientists get a light source that mimics solar radiation, some patients, and then they want to determine what is called the MED (minimal erythema dose…ie how much light makes them turn red). Then they look at the MED in Sunscreen protected skin divided by MED in unprotected skin.

This ratio is called the SPF or the sun protection factor.

So for example, an SPF of 15 would allow 15 times as much time in the sun to cause the same level of redness compared to if no sunscreen had been.
Now to translate this, there are scientists who incorporate these numbers into fancy graphs…

uv filtering







So what we know is that an SPF of 15 will block 93.3% of UV that reaches your skin and an SPF of 50 will block 98% of UV that reaches the skin. What is interesting is that because the SPF is calculated as a ratio, the level of UV that you can block really levels off around an SPF of 30-50. Any SPF higher than this doesn’t add a lot more photoprotection.
Because these ratings are looking at the level of redness created in the skin, or sunburning, they mostly pertain to UVB protection.
Now we know that UVA is responsible for the photoaging changes that we all want to avoid, but it turns out it is more difficult to measure the effects of UVA on the skin.
If a sunscreen label tells you it is “BROAD SPECTRUM” what you know is that UVA coverage is included as well as UVB coverage. So that is what you want to look for. The SPF of 30 or higher and the words “Broad Spectrum” can leave you feeling like you have purchased a sunscreen worthwhile.

Now in addition a sunscreen may comment on the level of water resistance (water resistance (40) or water resistant (80) which means the number of minutes where it is thought to effectively remain on the skin with water exposure.

There are really two main groups of active ingredients in sunscreens that protect you:

 1. “chemical” sunscreens that act to absorb UV radiation
2. “physical” sunscreens that both absorb and scatter UV radiation.

When we discuss physical sunscreens it may bring to mind the 1990’s and people hanging out on the beach with white paint on their noses.

These days, the ingredients in physical blocking sunscreens have been micronized and at times are added to gentle tints to allow for superior blending while giving you a nice and effective product.
The two main widely available ingredients in the physical sunscreen category in Canada include Zinc Oxide and Titanium Dioxide.

Titanium Doxide and Zinc Oxide provide full broad spectrum protection to both UVB and UVA. The majority of the sunscreens that we offer at our clinic contain these ingredients as they are effective and non-irritating.

When referring to Chemical sunscreens, some sunscreen ingredients are meant to target UVA (remember, aging…) like benzophenone, Avobenzone, Tinosorb S, and Mexoryl.
Other ingredients target UVB (or burning) like Padimate O, Octocrylene, Octinoxoate, and Salicylates. Just to name a few.
There are some chemical ingredients that are thought to be great combo filters for both UVB and UVA protection such as Helioplex or Mexoryl technologies.

The next important consideration in choosing your sunscreen is the vehicle (which is a fancy way of saying, how is it delivered onto your skin), such as lotions, creams, gels, sprays, sticks and lip balms. It is important to choose a vehicle that is right for you and to keep in mind that some vehicles can exacerbate already existing acne, like thick heavy creams.

If decide to go for the spray, just remember that it is easy to have spotty coverage, so you may want to rub the spray in with your hand after application or apply a second layer. I never recommend using sprays on the face. You can apply the spray into your palms and then rub it on.

In case sports are your thing, do look for sports-specific versions, as they tend to adhere better in the face of an unrelenting sweat down-pour.

One fun tip for application of sunscreens onto children, which was invented by my amazing husband, who likened trying to put sunscreen onto our children’s faces to alligator wrestling, Is you can pretend the kids are getting their faces painted. He will ask my 3 and 5 year olds what animal they want to be today. Then paint the sunscreen into my sons’ lion whiskers and then rub it all in as he roars away out the door, and then gives my daughter her leopard spots and then rubs it all in as she giggles into her sun hat.

If you have sensitive skin and find you are reactive to sunscreens, it can often be related to the added fragrances, preservatives, or even rarely to the organic chemical ingredients. In this case, look for unscented, hypoallergenic sunscreens that are labelled as “chemical free”. These contain physical blocking sunscreen ingredients like zinc oxide and titanium dioxide which are much less likely to cause reactions.

You should apply sunscreen generously and evenly before sun exposure.
Remember those lab studies I talked about earlier? Those SPF numbers are based on scientists being sciency, with all the time in the world to thickly and evenly apply the sunscreen in a manner than doesn’t directly translate to reality.
We know that in actual practice, people tend to use WAY less sunscreen than they apply in the lab studies, in fact 25-50% less. Which means that the amount of SPF you have on your skin is likely a lot lower than the number on the bottle if you haven’t used enough. An SPF 30 might mean you have only have an SPF 8. A shot glass size amount of sunscreen is required to cover an adult’s skin. This is equivalent to 2 tablespoons or 30ml.

If used properly, it means that your sunscreen bottle won’t have a chance to expire.
Which, by the way they do. Always respect a sunscreen’s expiration date. (I can tell you that from experience)

The chemical ingredients in sunscreens breakdown over time and also if you have forgot them somewhere warm where they can bake, like the trunk of your car on a hot day. Reapply after swimming, after sweating or exercising or every 2-2.5 hours. Don’t forget your lower lip, ears, and scalp as these are common areas where we see and treat skin cancers.

Other things to consider:

  • 60% of the day’s total UV will be in the 4 hour period around noon. So try not to spend time in the direct sun during these hours.
  • 90% of UV light will still come through light cloud cover
  • UV light reflects off of water, sand, snow, and concrete
  • Hanging out in the shade will only reduce 50% of UV exposure as it blocks direct rays but not reflected rays.
  • UV light increases at altitudes.

I hope you have found this to be helpful in understanding why dermatologists recommend sunscreen and that you can navigate your choices with some better understanding.

Dr. B. :0)