Skip to contentSkip to search
TELUS Health logo
TELUS Health logo

A complete guide to sunscreen and sun protection

Personal · Jun 12, 2020

by Amra Dizdarevic

Everyone looks forward to the warm summer sun and the outdoor sports and activities that accompany it. While the UV radiation from the sun provides us with many benefits, there are important risks to keep in mind with overexposure.

UV radiation reaches the earth from the sun in the form of UVB and UVA rays. UVB radiation plays a key role in skin cancer while UVA rays, which penetrate the skin more deeply, are associated with wrinkling, leathering, and sagging.

Avoiding sun exposure is the best way to protect yourself from UV radiation, but this is not always possible. Clothing is our first line of defense against the sun’s harmful UV rays and protects us by absorbing or blocking much of this radiation. The more skin you cover, the better.

Your next line of defense is sunscreen. Sun Protection Factor (SPF) is a measure of a sunscreen’s ability to prevent UVB from damaging the skin.

Here’s how it works: it takes 20 minutes for your unprotected skin to start turning red. Using an SPF 15 sunscreen theoretically prevents reddening 15 times longer – about five hours.

Another way to look at it is in terms of percentages: SPF 15 filters out approximately 93 per cent of all incoming UVB rays. SPF 30 keeps out 97 per cent and SPF 50 keeps out 98 per cent. The difference may seem negligible, but for light-sensitive individuals, or those with a history of skin cancer, those extra percentages will make an important difference. Furthermore, higher SPF values offer some safety margin, since most people generally do not apply enough sunscreen.

Top sunscreen Do’s & Don’ts:

1. Do choose an SPF of no lower than 30 and no higher than 50, with at least three of the following active ingredients: salicylates, and/or cinnamates for UVB absorption; benzophenones (such as oxybenzone) for shorter-wavelength UVA protection; and avobenzone, ecamsule (Mexoryl), titanium dioxide, or zinc oxide for the remaining UVA spectrum.

2. Do choose a water-resistant sunscreen that will stay put on hot days, while playing sports, or if you spend a lot of time outdoors. These sunscreens are less likely to drip into your eyes when you sweat.

3. Do use enough. To get the full SPF of a sunscreen, you need to apply one ounce – about a shot glass full. Most people apply only one-half to one-quarter of that amount, which means the actual SPF they have on their body is lower than advertised. To allow ingredients to fully bind to the skin, apply 30 minutes before sun exposure.

4. Don’t forget to reapply. No sunscreen, regardless of strength, should be expected to stay effective longer than two hours without reapplication. It should also be reapplied immediately after swimming, toweling off, or sweating during sports.

5. Don’t rely solely on a high SPF. Products with very high SPFs can create a false sense of security, prompting individuals to stay out in the sun longer and neglect other sun-protective behaviors, like seeking the shade and wearing sun-protective clothing. However, sun damage (for example, UVA damage, which not only accelerates skin aging, but also contributes to skin cancers) can take place without skin-reddening doses of UV radiation.

6. Do look for the new seal of recognition for proper UVA & UVB protection. Only a sunscreen with a UVA protection factor that is one third of the UVB protection factor can possess the new seal of recognition issued by Health Canada. When buying a sunscreen ensure that it states: UVA + UVB protection or contains this new seal of recognition:

7. Don’t expose children under the age of six months to either the sun or to sunscreen. Shade and protective clothing are the best ways to protect infants from the sun.

8. Do wear sunscreen daily, including cold or cloudy days – up to 40 per cent of the sun’s UV radiation reaches the earth on a completely cloudy day.