This year marks the 10th anniversary of the great sunscreen speech hoax. In case you missed it: in 1997, everybody seemed to be quoting Kurt Vonnegut's advice to graduating MIT students that famously began, 'Wear sunscreen.' The trouble was - Vonnegut didn't write that or any other MIT commencement address. The only true part of the proposition, then and still? Sun damage is real. Skin protection is essential. Wear sunscreen!

It's one of the most frequent questions I get. Patients ask me all the time: Do I really need to wear sunscreen? And the answer is, "Yes, no matter who you are, where you live, where you work, you really need to wear sunscreen every day.' Why am I so determined to get everybody slathered with skin protection? Well, nobody is in a better position than a dermatologist to see the harsh effects of solar radiation on human skin.

Most people know that exposure to the ultraviolet (UV) rays of the sun can lead to skin cancer, especially in fair-skinned people with light eye and hair color. But it's not only pale folks who are at risk: multiple sunburns, for any skin color or type, raise the risk of skin cancer. And sunscreen really can effectively prevent sunburn, if you use it right.

Short of cancer, though, years of sun exposure gradually change our skin in ways that make us look - well, old. Yes, sunlight can promote premature aging of the skin, accelerating natural aging processes, weakening collagen, and causing the elastic fibers in skin to uncoil like a worn-out bedspring. And then - well, you know the rest. Your skin sags. Gravity takes over, the skin can't hold out, so down it comes.

Sun exposure also dries out skin and reduces its ability to hold moisture. The resulting lines and wrinkles sharpen the appearance of aging. And the cute, charming freckles that the sun brings out in childhood morph into the brown spots and discoloration that plague us as we get older.

So how can we use sunscreen to get the skin protection we need? First, be sure you get the right product. The worst sun damage comes from UVA rays. UVA has a longer wavelength, so it can penetrate deeper into the skin, causing the aging effects we associate with sun exposure. We now know that UVA exposure also blocks your skin's natural repair mechanisms, so that previous damage and pre-cancers cannot be reversed. It's UVA radiation that can give you a sunburn on a cloudy day - it travels right through the clouds. And it can go through the glass of your car windows, which is why we dermatologists see the most skin cancers on the head and neck, on the left. Look at the left side of your neck. Do you see brown spots? When you were 13, they didn't have UVA protection. That's the ray that's aging you.

So I always urge my patients to make sure they have the right product, and to use it correctly. First, look for a bottle or tube of sunscreen that blocks both UVA and UVB rays (UVB is the one that causes burning between 10 am and 3 pm). More tips for effective sunscreen use:

Be sure you get a sunscreen with an SPF number of at least 30

Apply it liberally, about 15 to 20 minutes before sun exposure

Reapply every one to two hours, especially if you're going into the water or perspiring a lot

Once you have the sunscreen part down, there's more you can do to protect yourself from the sun:

Limit your sun exposure, especially during the high sun hours of 10 am to 3 pm

Seek shade can whenever possible

Find sun protective clothing - it offers effective protection while you're outdoors

Throw away your sunscreen from last year and purchase new products

That last point needs some extra emphasis. Most people don't realize that these old sunscreens chemically break down. Unless there's an expiration date on the bottle, you can't assume they'll provide the label's SPF protection for more than a year.

For the take-home message, I'd just like to elaborate on the advice of journalist Mary Schmich (she's the one who really wrote the 'Vonnegut speech'), and urge everybody to use sun protection that blocks both UVA and UVB to their exposed skin each and every day. In other words - "Wear sunscreen!"