They penetrate glass. They penetrate clouds. Their power is the same on a dull winter day and the sunniest summer day. They damage your skin, leading to aging and skin cancer.

What are they? UVA rays.

Ultraviolet rays
Ultraviolet (UV) light is divided into UVA, UVB and UVC. For years, our attention has been focused on UVB, the cause of sunburn. The SPF rating on your sunscreen refers to the UVB protection specifically. Unfortunately, many compounds used in sunscreens today that have good activity against UVB have little or no activity against UVA. UVC is almost completely filtered by the ozone layer so it is not an issue at present, except at high altitudes.

UVA has more penetration ability than UVB. It goes deeper into the skin as well as passing easily through window glass so your skin can be damaged even when you are driving in the car with the windows closed. Because UVA can penetrate to the deeper layers of the skin, it has a more damaging effect on the skin structure causing loss of collagen and elasticity of the skin, which results in sagging and wrinkling.

We often see that people who spend a lot of time driving have more damage and wrinkles to the left side of their face because that side of the face is receiving more UVA rays from the driver’s side window.

The good news is that you can protect your skin from UVA rays as well as UVB but you cannot use the SPF rating of the product as a guide for UVA protection.

Sunscreens have come a long way since the irritating PABA compounds that I used in university. Now you can have physical sun blocks, chemical sunscreens or a combination of the two.

Physical sun blocks
The advantages of the physical sun blocks include their high level of protection and their low likelihood of causing irritation. The 3 most important physical sun blockers are titanium dioxide, zinc oxide and iron oxides. If you’ve ever used a zinc-containing compound on a baby’s diaper rash, you have an idea about the disadvantages of these compounds: they are visible on the skin. Of course, they’re not as opaque as diaper rash cream because they are ground to microscopic particles, a process called micronizing but pure physical sunscreens tend to look chalky or have to be tinted to match your skintone.

Chemical sunscreens
Chemical sunscreens tend to be clear and colourless on the skin and often have physical properties that improve the texture of the final product such as emollient effects. Each compound specializes in absorbing a particular wavelength of light and none provides complete, full-spectrum protection so a good sunscreen usually requires a mixture of chemical sunscreens or a chemical compound blended with a physical blocker.

Look for avobenzone in your chemical sunscreen to be certain of good UVA protection. Micronized zinc oxide is the physical blocker that provides excellent UVA protection.

Added benefits of sunscreens
In addition to UV protection, we now expect our sunscreens to do a lot more for our skin. For instance, good sunscreens provide active cell protection in the form of anti-oxidants and chelating compounds. These ingredients protect the skin from damage caused by pollution and wind, in addition to sun.

Finally, the critical factor that determines the effectiveness of your sunscreen is you. You need to apply the sunscreen carefully to all of your exposed skin and remember to reapply it every 2 hours during sun exposure. If you want to know how well you are applying your sunscreen, we can do a UV photograph that will show where the product is on you skin.