With sunny weather having finally arrived, more people are heading to the drugstore to buy sunscreen for themselves and their families. There are so many products on the market today that the choosing one can seem daunting. Fortunately, selecting a sunscreen that provides excellent sun protection doesn't have to be complicated; it boils down to looking closely at the bottle's label for one of a few key ingredients along with the SPF.
There is irrefutable scientific evidence that the sun's ultraviolet (UV) rays cause skin cancer, premature aging, cataracts and suppression of the immune system. Skin cancer rates have skyrocketed over the past 50 years, and there are now more cases of skin cancer each year than of all other cancers combined. Sunscreens play an important role in protecting our skin from sun damage, and research has shown that their use can reduce the risk of both non-melanoma skin cancers and of the more dangerous melanomas.
The ultraviolet radiation that reaches the earth from the sun is divided in to UVB and UVA. UVB causes sunburn and skin cancer, while UVA rays contribute to the development of sunburn and skin cancer, and are thought to be the primary cause of skin aging. Despite the fact that we are exposed to approximately 20 times more UVA than UVB, the vast majority of sunscreens worldwide are biased toward UVB protection, in part because most active ingredients protect in this range. The SPF, found on every bottle of sunscreen, reflects protection from sunburn and gives consumers only a little information on whether a product defends against damage from "silent" UVA rays.
2012 brought new regulations in to place in Canada and the US that require a product meet a certain threshold of UVA protection in order for its manufacturer to claim it is "broad-spectrum". While this is a vast improvement over the situation prior to 2012, above this threshold sunscreens vary significantly in their ability to filter out the longest and most deeply-penetrating UVA rays (known as UVA I).
Sunscreen active ingredients (known as UV filters) work by absorbing, scattering and reflecting the sun's ultraviolet rays. They have traditionally been divided into chemical (organic) and physical (inorganic), based on the properties of the molecules. Of the 22 UV filters than can potentially be found in sunscreens sold in Canada, the following provide the highest degree of protection from UVA I rays. (Note that UV filters may also be listed on labels under one or more alternate chemical or trade names.)
1. Avobenzone. Introduced in the 1990s, avobenzone was the first chemical UVA filter. Its usefulness was originally limited by its lack of photostability, which means that avobenzone is degraded by sunlight. Manufacturers have largely overcome this issue by combining it with other ingredients that stabilize it, preventing its breakdown. It remains a highly effective UVA filter and 2-3% of avobenzone can significantly boost the degree of UVA protection a sunscreen provides.
2. Ecamsule is a stable UV filter that provides protection through much of the UVA range. It is often combined with drometrizole trisiloxane, a stable broad-spectrum UVB/UVA filter. A number of products sold in Canada contain Ecamsule in combination with avobenzone, resulting in a high degree of UVA protection.
3. Bemotrizinol and Bisoctrizole are two stable broad-spectrum filters that protect in both the UVA and UVB ranges. They are often combined and provide excellent broad-spectrum protection. Along with zinc oxide, bisoctrizole is unique in that it protects across the entire UV spectrum. Because they are not yet on Canada's sunscreen monograph, these two filters are currently only available in a handful of products found on Canadian shelves (they are widely available in Europe, Japan, Australia and South America).
4. Zinc Oxide is a physical filter that has long been used for sun protection. It is often combined with titanium dioxide, another physical filter, in products labelled as "natural". Zinc oxide is stable and gentle, making it a good choice for young children and for those with sensitive skin. It also has a safety record that stretches back hundreds of years.
In its native form, formulations of zinc oxide leave a white cast on the skin. These were the original "sunblocks" that lifeguards used on their noses. "Micronized" formulations have been developed in which the particles are so tiny that they reflect less light and as a result do not leave a white film. Zinc oxide's main drawback is that it is a less efficient UV filter than the chemical sunscreens, meaning that it is difficult for manufacturers to achieve very high levels of protection when zinc oxide is used alone.
Most sunscreens will contain between two and seven UV filters, some of which absorb in the UVA range while others absorb primarily in the UVB range. These are combined with other ingredients such as moisturizers and preservatives. A plethora of options exist today, and sunscreens can be found as creams, lotions, gels, sticks/bars, sprays and powders. In addition, UV filters are now routinely added to moisturizers, making it easier than ever to protect your skin from the sun on a daily basis.
Ultimately the best sunscreen is the one you will use. If a sunscreen is heavy or oily, you may be less likely to apply it in the generous proportions needed to achieve adequate protection. The vehicle plays an important role in this, with lotions tending to be lighter than creams or products labeled as "sport" or "water-resistant". Because most UV filters are dissolved in oil, higher SPF products tend to be heavier than those with lower SPF values.
Experiment with the consistency of different products, looking for a "broad-spectrum" product with an SPF of 30 or higher that contains at least one of the above ingredients. Use approximately 1/2 tsp for the face and neck and 2 tbsp for the entire body. Re-apply every two hours, and more frequently if you are immersed in water. Finally, remember that sunscreen is only part of a good sun-protection program that includes wearing hats, sunglasses and sun-protective clothing, as well as seeking shade. Make the investment in taking care of your skin early; it will thank you later in life!