If you look ‘under the hood’, sunscreen is quite fascinating. According to this article from TheConversation.com, it contains two categories of active ingredients: UV absorbers and UV reflectors.
UV absorbers are chemicals that, as the name suggests, ‘absorb’ UV rays so that our skin doesn’t have to. UV reflectors are blockers (like titanium dioxide and zinc oxide) that create a physical barrier between the skin and UV rays.
Depending on the active ingredients they have, some sunscreens absorb the UVB part of the spectrum, while others absorb the UVA part. So, which offers the best protection? Sunscreen labelled ‘broad spectrum’ can protect you from both UVA and UVB.
The Sun Protection Factor (SPF) estimates the degree of protection of a sunscreen. To give you an idea, an SPF of 30 means that it would take a person 30 times longer to ‘burn’ when wearing sunscreen than the person would without it. This is because only one-thirtieth (or 3.3 per cent) of UV radiation is allowed to reach the skin. Similarly, an SPF of 50 filters 98 per cent of UV, and only one-fiftieth (or 2 per cent) gets through.
That’s right – sunscreen has a shelf life. So, if you find an open bottle in a drawer or your beach bag, before using it, you may want to check the expiration date and storage conditions on the label. According to HealthNavigator.org.nz, most sunscreens should be stored below 30ºC and last about two to three years.
So, what happens if you use expired sunblock? Dermatologists say that expired sunscreen can be less effective at preventing damage from UV light, as expired products don’t guarantee the SPF listed on the label. The bottle may also harbour bacteria, which can potentially lead to skin irritation.
The Health Promotion Agency recommends applying about one teaspoon of sunscreen on each of these areas: face, ears, neck, each arm, each leg, and the front and back of your body. It’s also a good idea to apply two coats, one 20 minutes before you step outside, and a second one after you’ve been outside for 10 minutes – just in case you’ve missed any spots the first time.
Then, make sure you reapply sunscreen at least every two hours, or even more often if you’ve been in the water or have worked out. And as much as possible, cover up and stay in the shade, especially during the central hours of the day (10 am to 4 pm).
We hope you enjoy the remainder of the season. And of course, if you have any questions for us, we’re here to help.
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