5 surprising facts about sunblock

It’s a beautiful sunny day and you’re planning to spend the day outdoors. You can already feel the sun’s warm rays caress your skin. Hat, sunglasses, snack, water bottle... you’re ready to go. Hold on! What about sunscreen?

You fish out an old tube from last year, but there’s an expiry date on it. So what, it’s just marketing, right? Not so fast!

What’s the straight dope on sunscreen? Here are five facts about sunscreen that may surprise you.

First off, what does the expiry date mean?

1. If the expiry date is past, best to throw it away.

The expiry date will vary from one product to the next. However, over time the chemical and physical ingredients break down and become less effective. According to the Canadian Dermatology Association  (This hyperlink will open in a new tab)., you should pay attention to the expiry date.

Know that extreme temperatures affect effectiveness. If your sunscreen’s colour, smell or texture is different, throw it out.

2. Sunscreen is not just for summer...

Consider applying sunscreen year-round.

In winter, the snow reflects UV light. The next time you go skiing, count the number of raccoon faces you see at the après-ski bar. Those people didn’t use sunblock.

Don’t be fooled by cloudy days in the spring and fall. Use sunscreen to protect yourself from harmful UVA and UVB rays. UVB rays, which are absorbed by the ozone layer and clouds, are the main cause of sunburns. UVA rays, however, penetrate the ozone layer and clouds. They cause premature aging, and are also a cause of skin cancer.

So, you think you’re safe in the shade? Think again. Obviously, a tree or parasol will protect you from direct sunlight, but not necessarily indirect sunlight. Snow, water and light-coloured smooth surfaces (like concrete) expose you to UV rays by reflecting them.

3. Wait, what? So, I have to apply sunscreen indoors?!

Yes. Experts recommend applying sunscreen indoors when you are exposed to UV rays through a window. This also goes when riding in buses, cars, trains and planes.

Window glass may block UVB rays, but not UVA. Studies have shown that daily exposure to UVA rays, even through a window, can make your skin look five to seven years older.

UVA rays are not responsible for tanning or burning because they penetrate the skin more deeply. This means that your skin will look dull, and patches will appear.

4. SPF 60 or 100: now that’s marketing!

SPF is the product’s ability to block UV radiation. However, it’s important to know that the sun protection factor (SPF) is measured in a lab.

Know that no sunscreen currently on the market can block 100% of all rays. The data presented below speaks for itself: an SPF of over 50 doesn’t mean double the protection!

Protection Factor
SPF 15

SPF 30

SPF 50


Percentage UVB blocked




In Canada, since 2014, manufacturers are prohibited from indicating an SPF over 50 on their products. The reason is that higher SPFs give a false sense of security, so people tend to expose themselves for longer periods.

That being said, sunblock designed for sports activities or that are water-resistant adhere better to the skin. They tend to last 40-80 minutes. This is great for swimming! This also applies to perspiration.

The Canadian Dermatology Association recommends using SPF 30 sunscreen (minimum). Opt for a broad-spectrum one. This means that it also blocks UVA rays, which is not the case for all products.

5. Not all ingredients are made equal.

Sunscreen contain harmful ingredients. This is definitely a controversial topic.

Obviously, the consensus among dermatologists is that sunscreen is useful for protecting yourself from the harmful effects of UV light. There is debate, however, over which ingredients are best.

This boils down to choosing between chemical and physical sunscreens  (This hyperlink will open in a new tab).. Chemical filters, like avobenzone and octocrylene, absorb high-intensity UV radiation and convert it to lower-energy wavelengths. Physical filters, like titanium dioxide and zinc oxide, reflect or refract UV radiation. The Canadian Cancer Society  (This hyperlink will open in a new tab). lets users decide for themselves which one they prefer.

Apply enough (about a shotglass worth) to your entire body at least 30 minutes before going out into the sun. Reapply every two hours or more when swimming, with:

  • 30 ml or 2 tablespoons for the body, without forgetting the back of the hands.
  • 5 ml or 1 teaspoon for the face. Don’t forget your neck, ears and scalp.
  • Apply lip balm with SPF. Reapply after eating or drinking.

Incorporate sunscreen into your daily routine because an ounce of prevention is worth a pound of cure! Limit your exposure to direct sunlight from 11 am to 3 pm. Wear sunglasses with UV protection and a hat.

Even dark skin needs protection. As for the notion that a base tan protects you against sunburn... it’s just a myth.