Sunscreen – what to buy, how to apply



After a long Canadian winter, most of us look forward to summer and spending more time outdoors. Naturally, this means more exposure to the sun’s rays and their potentially harmful effects. A few proven methods of sun protection can help alleviate our well-founded concerns about UV exposure. And while it is recommended that sunscreen should be worn year-round, summer is a great time to get into the habit of making sunscreen part of your daily routine.

By Dr. L. Alexandra Kuritzky and Dr. Jennifer Beecker

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Sunscreens are designed to protect us from ultraviolet (UV) radiation. Of the three types of UV rays emitted by the sun, only UVA and UVB reach the earth’s surface. The level of UVB changes over the course of the year and throughout the day, and is highest in the summer around noon when the sun is at its peak. The UVA level is much more constant throughout the year
and the day.

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While we’ve been aware of the fact that UVB causes sunburns, premature aging of the skin and skin cancer for some time, we also now know that UVA contributes to the development of skin cancer and UV-induced aging. For all these reasons, it is important to choose a sunscreen that protects from both UVB and UVA and to apply it properly to get full benefits.  

Which sunscreen is right for me?
Start by choosing a sunscreen that is labelled “broad spectrum,” with a sun protection factor (SPF) of 30 or higher. The SPF measures the amount of UVB blocked by the sunscreen. In simple terms, an SPF of 30 means that it takes 30 times longer for the skin protected with sunscreen to burn compared to unprotected skin. An SPF of 30 blocks almost 97 per cent of UVB if it is applied properly.

The term “broad spectrum” is just as important – it means the product meets Health Canada’s requirement to block a specified amount of UVA.
Remember as well, if you are going to be swimming or sweating, choose a sunscreen that is labelled “water/sweat resistant 40 minutes” or “water/sweat resistant 80 minutes”– these products have been tested to maintain their effectiveness after 40 or 80 minutes of water immersion.

To help simplify your choices, look for the Canadian Dermatology Association (CDA) logo, which offers an assurance that the sunscreen meets the CDA Sun Protection Program’s standards.

How much do I need to apply?
The most common mistake people make in sunscreen application is not using enough. Studies show that most people apply only one-quarter to one-half of the amount of sunscreen that was used in determining the SPF of the product. As a result, they receive only a fraction of its protection. This means most people apply an SPF 30 sunscreen in a way that may only give them an effective SPF of 10.

To get the protection the SPF promises, you need to apply the amount that was used when the product was tested in the lab. This means applying one full teaspoon (5 ml) to the face, ears and neck, one teaspoon to each arm, two teaspoons to the torso and two teaspoons each to the legs when wearing a swimsuit, which means a total of nine teaspoons (45 ml) to cover the whole body.

That seems like a lot of sunscreen. Do I still need to re-apply it every two to three hours?
There is evidence that the best time to apply sunscreen is before sun exposure, and again within one hour after sun exposure begins to provide the highest level of protection. This second early application helps you to reach the amount necessary to fully protect your skin and also ensures you cover any areas of skin that were inadvertently missed the first time.

In a study of people who were relatively inactive, properly applied sunscreen maintained 75 per cent of its SPF after eight hours. Another study testing sunscreen after a day of outdoor activity showed that the SPF retained about 60 per cent of its original value at four hours, and about 45 per cent at eight hours.

When you apply an SPF 30 sunscreen, after four hours of activity your protection level will approximately reach an SPF of 18, and after eight hours, the SPF will be about 13. The study showed that the necessary frequency of reapplication depends on the type of activity you are engaged in. Reapply after swimming, sweating, towelling or rubbing since these activities remove sunscreen from the skin’s surface. For lengthy times outdoors, at least one reapplication during the day seems prudent.

Is sunscreen the best way to protect my skin?
Sunscreen is one part of a good sun-protection strategy, which should also include a hat with a wide brim, sunglasses (wrap-around styles are best) and sun protective clothing – ideally long sleeves and pants or a skirt with a tight weave. When this is not practical and for areas most people don’t normally cover – such as the face – sunscreen is your best option. In addition, try to plan your outdoor activities to avoid the peak hours of exposure, between 11 a.m. and 3 p.m.

How can I best protect my kids?
Sun damage accumulated at a young age can contribute to the development of skin cancers later in life. Childhood is probably the most important time for paying attention to sun protection – it’s also a great opportunity to teach your children about sun-protection practices and build healthy habits. Wide-brimmed hats, wraparound sunglasses and long-sleeved sun-protective clothing are essential. Luckily, there is a wide range of sun-protective clothing available for active children, especially in outdoor activity shops.

For areas that cannot be covered, the tips outlined above for sunscreen selection are more important than looking for a sunscreen labelled “kids” or “babies”. All sunscreen ingredients approved by Health Canada are approved for use in children six months of age and older. It is recommended to keep children under the age of six months out of the sun.
Children and those with sensitive skin tend to better tolerate physical sunscreens with the active ingredients zinc oxide and titanium dioxide.

Enjoy the outdoors safely this summer – your skin and health will thank you for years to come. n

Dr. Jennifer Beecker is the Chair and National Spokesperson for the Canadian Dermatology Association Sun Awareness Program. She is Research Director for the Division of Dermatology at The Ottawa Hospital, and Assistant Professor at the University of Ottawa. (

Dr. Alexandra Kuritzky is a final-year dermatology resident at the University of Ottawa and a mother of two young boys. She is passionate about sun protection education. Dr. Kuritzky plans to establish her practice in Vancouver, British Columbia.

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