Why can you still be affected by UV rays when it is cloudy?

Question

And how does sunblock protect you?

Answer 1

Don't let fear of insufficient vitamin D keep you from using sunscreen.

"The reality is you need about five minutes of sun exposure, three to four times a week, on an area the size of your face or hands," says dermatologist Mark Lupin, regional director of the Canadian Dermatology Association.

Any more than that, and your skin stops making usable vitamin D and starts making an inactive form that won't do you any good anyway, says Lupin.

"On balance, it's better to minimize the risk of skin cancer," Lupin says. "Put your sunscreen on and don't worry about the vitamin D."

Some people, such as the elderly and very young with very limited sun exposure, may need vitamin D supplements in the winter. Vitamin D is important for bone and muscle health, as well as prevention of certain kinds of skin and other cancers, Lupin says.

Sunscreen will prevent sunburn, premature aging of the skin and protect from some forms of skin cancer. Although to date, Lupin says there is only indirect evidence that it protects against melanoma, the deadliest form of cancer.

"The Number 1 risk factor for melanoma is the number of moles you have," Lupin says. "And the No. 1 thing that can minimize the number of new moles is sun protection."

The sun is to blame for up to 80 per cent of the skin damage that results in premature aging and wrinkling.

Not all sunscreens are equal, Lupin says.

"What really separates them are how stable they are in the sun, and how well they screen for UVA rays," he says.

Five or six years ago, Ombrelle was "far and away the gold standard of sunscreens," but today, a number of brands offer the same level of protection, Lupin says.

How do you choose among the myriad products on store shelves?

- Make sure the product provides UVA or "broad spectrum" protection. Both UVB and UVA rays cause problems ranging from skin cancer to premature aging and wrinkles, but in general, UVB is associated with burning, and UVA with aging.

- Buy SPF 30 or higher. Most people only use enough sunscreen to benefit from half the SPF number on the bottle, Lupin says. Aim to use two tablespoons to cover an entire body.

The Sun Protection Factor rates the ability of a sunscreen to allow you to stay in the sun without burning. SPF 15 would allow you to stay in the sun 15 times longer than without sunscreen protection.

If used properly, sunscreen rated SPF15 will protect you against 93 per cent of UVB rays. SPF 60 will protect you against about 98 per cent of UVB rays.

- Sunscreens degrade in the sun. Some are more stable than others, but it is difficult for people to know one from another. Get professional advice, or, since most sunscreens last three to four hours, simply plan on reapplying frequently.

- More expensive does not necessarily mean better. You may be paying for packaging, Lupin says.

- There are many proprietary formulations on the market with varying effectiveness. The simplest solution is to buy a sunscreen that carries the Canadian Dermatology Association logo. The CDA recognizes 16 brands.

- If you're going to be very active, a "sweat proof" product will last 80 minutes if you sweat or swim, and a "sweat resistant" product will last 40 minutes.

- If you have eczema, allergies or are sensitive to scent, choose a product with light or no fragrance. Some advocacy groups say fragrance-free products are less likely to contain carcinogens. The Environmental Working Group, a non-profit research and advocacy group, has just published a rating of 785 sunscreens for safety and effectiveness.

- A "chemical-free" sunscreen contains titanium dioxide or zinc oxide which, technically, are elements rather than chemicals, Lupin says. These products have improved in recent years and are less white and pasty than earlier formulations.

- Avoid alcohol-based products if you have dry skin. Aerosols are likely to be alcohol based. Pump products are not. If you sweat a lot, try a silica based product.

Other things you can do:

- Try an antioxidant cream. A pharmaceutical grade vitamin C lotion applied daily to skin can repair initial, minor sun damage, Lupin says. It provides just SPF 6 protection but lasts 24 hours.

"It doesn't take the place of sunscreen, but fills in the gaps, Lupin says.

A vitamin C and E combination is best because vitamin E can replenish the vitamin C as it degrades in the sun. You want a product with 10 to 20 per cent vitamin C, but it's hard to be sure you're buying the right stuff. Many vitamin C and E lotions either contain too little of the vitamins to be of use, are not very stable, or don't penetrate the skin well, Lupin says. Vitamin C ester is not as effective as regular vitamin C. A product labelled "vitamin C 30 per cent" may not be in a form that can be absorbed into the skin.

Consult a dermatologist.

- A tan offers the equivalent protection to a sunscreen with SPF 3 or 4, Lupin says.

"That's a tiny bit of protection but it's not enough. You can be lulled into thinking you're safe, but you're not."

- UV levels are much higher in thin atmospheres, so remember that a light overcast day on top of a mountain can be just as dangerous to your skin as a hot sunny day at the beach in the city.

Wear protective clothing, long sleeves, wide-brimmed hats and wrap-around sunglasses. Avoid the sun from 11 a.m. to 4 p.m. Tightly woven fabrics provide more protection. Dark, heavy denim has an SPF of 1,700. Wear denim and you'll be able to stay in the sun 1,700 times a long as you would if you were buff naked.

Clothing made of sun protection fabrics may be more pleasant for young children and outdoor workers than wearing a lot of sunscreen. The cost has come down in recent years and the protection is good, Lupin says.

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Answer 2

Yeah.

Answer 3

Because UV rays can penetrate clouds.