Chemist Corner

By Louise Hidinger, Ph.D.

Summer is now in full swing and with people shedding layers and flocking to the outdoors, sun protection is an absolute must. When it comes to topically applied sun protection products, there are two types of active ingredients, synthetic sunscreen chemicals, and physical blockers. Synthetic sunscreens are man-made chemicals that have the ability to absorb and disperse the energy of UV radiation, whereas physical blockers are minerals that block UV radiation from reaching the skin. Despite overwhelming evidence that synthetic sunscreens provide safe, effective protection against sun damage, many people remain wary of them and turn towards ‘natural’ sunblocks, which contain only minerals, namely, zinc oxide and/or titanium dioxide.

Zinc oxide and titanium dioxide are readily available from soap-making and craft suppliers, and recipes for making sunblock creams and lotions abound on the internet. With the popular notion that “natural is better”, people may be tempted to make their own sunblock lotion, or else purchase handmade sunblock creams and lotions, sold by independent crafters at farmers’ markets and craft fairs. The problem with these handmade sunblock products is that zinc oxide and titanium dioxide are actually very difficult to blend into a cream/lotion base, and once blended in, it is even more difficult to keep them evenly dispersed in the final product. The particles of zinc oxide and titanium dioxide have a strong tendency to clump together, and form aggregates. When applied to the skin, the resultant cream provides patchy coverage, covering only some areas of the skin while exposing other areas. This patchiness is not going to be visible to the naked eye, but it would be evident if the cream was tested in a laboratory for its SPF rating. Unfortunately, many of those who are whipping up sunblock creams at home are not going to go the trouble and expense of getting their products tested by a lab. Getting those tests done is extremely expensive and not within the budget of many independent crafters.

In order to adequately protect skin, a sunblock cream that contains only mineral oxides must provide even and thorough coverage. If you are thinking of purchasing a handmade sunblock cream, be sure to ask the maker if it has been tested to certify the SPF rating. And if you’re dead set on making your own sunblock, don’t rely on the supposed ratings given with recipes found on the internet. The only way to find out is to get the sunblock cream tested by a certifying laboratory to find out the SPF rating. (Chances are, the SPF rating will be a fraction of what it was expected to be.) Without laboratory testing, the only way to be sure it is providing adequate protection is if you can see a solid white coating on your skin!

Along with handmade sunblock creams containing mineral oxides, another natural-based trend is the use of coconut oil as a sunscreen lotion. Numerous “green living” websites and health bloggers tout coconut oil’s many benefits, including an average SPF of 10. Coconut oil provides only minimal sun protection, blocking about 20% of incoming UV radiation, and it does not provide broad spectrum protection against both UVA and UVB radiation. In comparison, both the Canadian Dermatology Association and the American Academy of Dermatology recommend use of a broad spectrum sunscreen with minimum SPF 30, which blocks 97% of incoming UV radiation. Coconut oil, and any other vegetable oil, does not contain chemicals that have the ability to absorb and disperse the energy of UV radiation. As a result, coconut oil cannot offer adequate sun protection.

When it comes to topical sun protection products, it really is worth it to buy a sunscreen from an established manufacturer that has been adequately tested, especially if it is for use on children, the elderly, or those with chronic skin conditions that require adequate sun protection. In any event, sunscreen products should always be combined with safe sun practices, including wearing a broad-brimmed hat, sunglasses, long-sleeved top and pants, staying in the shade, and limiting or avoiding activities during peak hours of daylight between 10 a.m. and 3 p.m.

About the Author Louise Hidinger is a Toronto-based cosmetic chemist.

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