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  • Dr. Henry Ngai

The Sunscreen Guide 2021





Pandemic has changed almost everything. It has certainly affected our lifestyle, both inside and outside our home. One important change is many of us no longer go to the workplace or classes. We spend long hours indoors and we do not venture out much. For many of us , sunscreen has lost its relevance as there is little need for sun protection when one stays home most of the time. However, as the pandemic is turning the corner and the precautionary social restriction is easing, people are once again eager to enjoy the outdoor, taking full advantage of Mother Nature and the lovely Summer weather. With a longer and sunny day, it is definitely not a good time to forget sun protection.


We have to accept total sun avoidance is not possible, nor is it desirable. Sunlight gives us a sense of well being, lifts our mood and helps to regulate our sleep wake cycle. The sun is important for vitamin D synthesis for healthy bones and immune system. However, too much sun is also harmful. The ultraviolet (UV) portion of sunlight has been shown to be a cause of 80-90% of skin cancers. Therefore, sunscreen is promoted to be an important means in preventing the disease.


Most people apply sunscreen to prevent sunburn and skin cancer, not realizing that it has an equal important function in reducing photoaging. In order to protect our skin properly from the sun, we need to have a good understanding of sunscreen. UV radiation (UVR) has 3 components, UVA, UVB and UVC. As UVC is mostly absorbed by the atmosphere, only 1% reaches us. A proper sunscreen, therefore, has to protect against both UVA and UVB.


Almost everyone knows the SPF means UVB protection factor. The higher the number, the more UVB radiation protection it confers. In Canada, any sunscreen that can block both UVA and UVB is labelled “broad spectrum “. In Asia and Europe, one can also see PPD (persistent pigment darkening) rating or PA (Protection Grade of UVA) rating, along with the SPF number on sunscreen labels. A broad-spectrum sunscreen is absolutely crucial as over 90% of the UVR that reaches the Earth’s surface is UVA. UVA is by far the more important UVR that is responsible for photoaging and carcinogenesis. It penetrates human skin deeply, more so that UVB. It causes more long-term skin problems than UVB. UVA is not filtered out by the atmospheric ozone, clouds or window glasses.



Sunscreen can safely be used on children older than 6 months. One should choose a broad-spectrum sunscreen with SPF 30 or higher. Health Canada does not recommend the use of sunscreen for children younger than 6 months because of the theoretical risk of increased absorption of sunscreen ingredients as a result of higher body surface-to -volume ratios and thinner epidermis. The mainstays of sun safety in infants include sun avoidance and protective clothing. Physical sunscreen is more preferable than chemical sunscreen in young children.


Recent studies have showed that sunscreen can be applied right before UV exposure without the need to wait for 15-20 minutes. It is important to apply adequate amount of product on the skin. Sunscreen should be re-applied frequently if it has a high likelihood to be removed, such as swimming, sweating, and wiping off by clothing.


If you are using other skin care product, you should always apply your sunscreen last. It is advisable to wait for 5-10 minutes for the other products to be absorbed first before applying the sunscreen.