KEY POINTS:
As summer approaches, we're all primed to slip, slop and slap. But how much do you really know about sunscreen?
Before you crack into that ancient bottle of sunscreen, here's something you might not be aware of: sunscreen, just like food, can go off.
In fact, it's only guaranteed to be effective for three years from its date of manufacture.
All sunblock should carry an expiry date, says the Cancer Society's Carolyn Shivanandan, and if your bottle is past that expiry date it's best to throw it out.
Beyond the expiry date, other key things you should check when buying sunscreen are that it's broad spectrum (protecting you from both UVA and UVB rays), that it's at least SPF30, and that it's water resistant.
If you don't know the difference between your UVAs and UVBs, the important thing to remember is that recent studies show they can both cause skin cancer.
Outside of that key fact, UVA rays are the ones time doesn't forgive. They penetrate deep into the skin, causing it to lose elasticity and wrinkle, making you look older.
UVB rays cause sunburn on the skin's surface.
And it's the SPF (sun protection factor) of your sunscreen that measures and controls the burn of UVB rays. In New Zealand, this can range from as low as SPF8 right up to SPF80.
Here are some other handy sunscreen questions and answers:
Should children use a different sunscreen to adults?
Because most brands have similar ingredients, it's more about the amount of fragrance and chemical loadings when choosing for children, rather than the degree of protection.
The best option is buying a sunscreen that's fragrance free.
A lot of products designed for children contain zinc oxide or titanium dioxide, which is the white layer that you see on the skin.
This doesn't absorb and it's useful for parents as they can see when to reapply the sunscreen.
Can you be allergic to sunscreens?
Sunscreen is like any skincare product in that there's not one sunscreen that's perfect for everyone. We all have different skin and react differently to exposure to the sun.
If you have an allergic reaction to a sunscreen, stop using it.
Try a different product, and if problems persist, visit a dermatologist - eventually you should find one your skin can cope with.
Does using sunscreen all the time put you at risk of vitamin D deficiency?
Although sunlight is the best source of vitamin D, between October and March most New Zealanders get enough sunlight in the daylight savings months via incidental sun exposure outside the peak hours of 11am-4pm.
From this exposure, the body is able to create sufficient amounts of vitamin D.
"Sufficient" is not the same for everyone, however.
Someone who burns easily may need only five minutes of sun exposure before 11am or after 4pm; someone who tans more easily or has darker skin will need up to 20 minutes.
Concerns about Vitamin D levels tend to be confined to the winter months when sun exposure naturally tends to be lower.
This is the subject of ongoing research.
How long before going outside should sunscreen be applied?
You should apply sunscreen at least 15-20 minutes before going out. Think of it like a coat of paint - you need to allow the paint to dry to form a film on the skin. Once outside, you should reapply every two hours or so.
Information supplied by the Cancer Society of New Zealand.
- Detours, HoS
