Here’s how to decipher the terms on your sunscreen label

Let’s be honest: Sunscreen is probably not the most exciting part of your skincare routine, but it is the most important. Its main job is to protect you from damaging ultraviolet radiation (also known as UV rays), which accounts for up to 80% of visible signs of aging in the skin. Even worse, damage from UV exposure is cumulative and increases your risk of getting skin cancer over time. According to the Canadian Cancer Society, melanoma, the most dangerous form of skin cancer, affected more than 8,000 people in Canada in 2020.

As a society, we’re more aware of layering on sunscreen in the summer, when the days are longer and temperatures rise, but it’s important to remember that sun care is actually a year-round necessity. The category can be a bit of a brain teaser, though. Before you select a formula, there are several factors to consider: What is SPF? What’s the main difference between UVA and UVB rays? What is broad-spectrum sunscreen? Not to mention, what are the best practices when applying—and reapplying—sunscreen?

Here, you’ll find explanations for the most common words and phrases found on sunscreen products and tips on how to choose sunscreen that suits your needs so you can approach the sun protection aisle with confidence.

What’s the difference between UVA and UVB rays?

Not all UV rays are created equal and understanding how each type affects the skin makes it clear why keeping all of them at bay is crucial. When sunlight passes through the ozone layer and reaches us, it’s mainly made up of two types of harmful rays: ultraviolet A (UVA) and ultraviolet B (UVB). The key difference between UVA and UVB rays are the wavelengths, which range from 290 to 400 nanometres; UVA have the longest wavelengths, while UVB have medium to shorter ones.

UVA rays are commonly referred to as the “aging rays” because they can penetrate the skin deeper than UVB rays, which means they affect cells deeper in the skin in both the epidermis & dermis and cause indirect sun damage through the creation of oxidative stress and can even alter our DNA. In translation, they cause the skin to age prematurely, resulting in age spots and wrinkles for example. They’re also associated with some skin cancers. About 95% of the UV rays impact our skin are UVA, and they penetrate windows and clouds. UVA rays are present all year round at a high intensity, and from sunrise to sunset which is a major reason why sunscreen is important every day of the year.

UVB rays, on the other hand, are referred to as “burning rays” because they emit a higher energy level that damages the outermost layers of the skin, causing sunburns. These rays are also linked to skin cancers. According to Health Canada, although UVB rays are present all year round, the intensity of UVB rays varies by season, location and time of day, with 11 a.m. to 3 p.m. being the peak hours.

What is SPF in sunscreen?

Everyone has heard of the three-letter abbreviation, but what does SPF stand for? The answer is “sun protection factor,” which refers to the number beside it, indicating how well the sunscreen protects skin against UVB (burning) rays. It measures how much solar energy is required to produce a sunburn on protected skin, but it’s complicated.

The number is an indicator of how much more protection you’ll have with sunscreen compared to your bare skin. For example, an SPF of 60 means that the sunscreen is giving you 60 times the protection that’s naturally in your skin, and it will take 60 times as much sun exposure for you to develop a sunburn. And that’s only if you are using it exactly as directed. However, we need to keep in mind that the SPF is not an indicator of time you should be spending in the sun.

Does higher SPF mean better protection?

The obvious question, then, is shouldn’t we all be wearing higher SPF sunscreen, like SPF 100? Not quite. First off, SPF is not a measure of how long you can be in the sun without reapplying. No matter how high the number is, it wears off in the same amount of time as lower SPF sunscreen. In other words, you still need to reapply it every two hours of sun exposure. In fact, both mineral and organic (chemical) sunscreens need to be reapplied generously every two hours, or after swimming, sweating or toweling off, to ensure adequate protection.

Wondering what number of SPF you should use? The Canadian Dermatology Association recommends using a broad-spectrum (UVB and UVA protection) sunscreen with an SPF of at least 30, which filters 97% of the sun’s UVB rays. If you’re wondering why dermatologists don’t just recommend that we use the highest-SPF sunscreen, consider this: The higher-SPF products are only slightly more effective at protecting you from UVB rays. For example, there is little difference between SPF 30 and SPF 50 when it comes to UVB protection. SPF 30 filters nearly 97% of UVB radiation, whereas an SPF 50 filters about 98%. Hence, an SPF 100 may create a false sense of security for the minimal incremental UVB protection it’s providing.

What does broad spectrum mean?

While your sunscreen’s characteristics can be left to personal preference, there are two things, according to the Canadian Dermatology Association, on which you shouldn’t compromise: an SPF of at least 30 and broad-spectrum protection. What does broad-spectrum SPF mean? Simply stated, it’s a term used to describe a sunscreen that protects against both UVB rays, which burn skin, and UVA rays, which cause damage like collagen breakdown, leading to premature skin aging.

It should be noted that a sunscreen’s SPF number refers mainly to the amount of UVB protection it provides. However, if a sunscreen has “broad spectrum” on the label, it means that it also has one or multiple filters offering a UVA protection. You can increase your chances of having optimal UVA protection by choosing a higher SPF formula. Another great tip is looking for the circled UVA logo which is approved by Health Canada and demonstrates that the sunscreen meets the minimum requirement for adequate UVA protection (PPD) in relation to the SPF. This is a ratio of 1PPD:3SPF. Another way to ensure you’re choosing effective sun care is to buy sunscreen recognized by the Canadian Dermatology Association.

How to apply sunscreen

According to the Canadian Dermatology Association, it’s best to apply a broad-spectrum sunscreen with a minimum of SPF 30 at least 15 to 30 minutes before venturing outside to allow the active ingredients to bond to your skin. If you’re planning on exposing a lot of skin (like wearing a swimsuit or running gear), apply it while you’re naked. This will help ensure you get complete coverage and that if your clothing shifts you won’t leave any exposed areas unprotected.

One of the most common question people ask is how much sunscreen to apply? The Canadian Dermatology Association says to apply “liberally,” but that can be interpreted differently. For full coverage, you should use about a teaspoon for your face (or two finger lengths) and a shot glass full for your body (35ml for the entire body & face). But it’s important to note that not everyone has the same size body, so plan to slather a layer over the areas exposed to sunlight and then massage it into the skin. Also, remember to reapply it every two hours of sun exposure, or after heavy sweating and swimming in which case you’ll usually need to reapply after 40 or 80 minutes.

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