Dr. Oz explains how cellulite is formed.

Tens of thousands of viewers have asked him medical questions, and now Dr. Mehmet Oz is ready with answers. When asking Dr. Oz a question, nothing is off limits!

What is cellulite? Do all women get it? How do we make it go away?

Dr. Oz says that if you have cellulite, point the finger at your family tree—the way your body stores fat is genetic. He says that fat cells, when they're doing their job, suck in as much fat as they can and then grow larger.

"It looks like a huge marshmallow," Dr. Oz says. "And these marshmallows begin to touch each other. And as they touch each other, they begin to push bigger and bigger and bigger molds of this stuff. … You put all this together, guess what happens? Cellulite."
Dr. Oz says anti-cellulite treatments don't really work.

There is a massive billion-dollar industry of anti-cellulite treatments, and Dr. Oz says all of the treatments—from creams and balms to procedures like rolling and smacking—have one thing in common: They don't really work. "You can't put a cream on and get inside the fat cell," he says.

While they may be able to give you a short-term reduction in appearance of cellulite—caused by swelling in blood vessels and tissue—"It doesn't hold," Dr. Oz says. "Here's one more bit of data: The guys don't care that much. They really don't."
Dr. Oz answers a question about varicose veins.

What causes varicose veins and spider veins? Is there a way to get rid of them?

Your heart pumps blood to fuel your muscle tissues. That blood returns to the heart, however, in a slightly different way. As you move your muscles, they milk the blood back up the veins. Valves in those veins ensure that the blood moves in the right direction. As you age, those valves can weaken, get pulled apart and leak. "As they leak, they fill those veins with too much blood. And they swell up and look like big worms," Dr. Oz says.

For large, painful varicose veins, Dr. Oz says you should have them removed. "If you're not having any problems with it, don't worry about it, it's not a big deal. But if you really don't like them or they're hurting a lot or they're unsightly, we have operations."

Dr. Oz says there are two common treatments—saline injections and lasering. The saline injections burn the walls of the veins, causing them to collapse so no blood can get in and making them disappear. Laser therapy works similarly by inducing scarring to prevent blood from reaching those same veins.

Why would you choose one procedure over the other? It depends on your skin tone, Dr. Oz says. For instance, lasering doesn't work as well on darker skin tones, he says.

Whichever treatment you choose, both are simple, don't require an overnight hospital stay and last forever, Dr. Oz says.
Jen asks how she can tell if the sun is damaging her skin.

How can I tell if the sun is damaging my skin?

Jen loves sunbathing and she thinks she looks better with "a nice glow." But how much sun is too much? "Getting enough sun is actually good for you. It builds up some of the nutrients that you have to have," Dr. Oz says. "The problem is we don't know when to stop."

target=_blank> Dr. Oz explains how skin works.  Watch

Everyone needs a little sun exposure—Dr. Oz recommends about 15 to 20 minutes per day. Without enough sunlight, the body might not build up enough vitamin D, which helps protect from cancer and possibly high cholesterol. "The sun turns cholesterol into vitamin D, so the body knows if it's not getting enough sun to elevate the cholesterol so there's at least a little bit there to get transferred to vitamin D," Dr. Oz says. Some people also suffer from Seasonal Affective Disorder (SAD), which means that they become depressed because they are not seeing any sunshine.

While some moderate exposure to the sun has benefits, Dr. Oz says sunbathing or tanning for hours is a serious health risk. Without protection, the sun's harmful ultraviolet rays can penetrate straight into your skin, causing sunburn, skin cancer and aging.

One sun worshipper gets tested for skin cancer .

"If you get too much sun, the sweat glands shrivel up—the sweat, of course, dries up. The skin itself begins to get desiccated," Dr. Oz says. "You're destroying this covering, and therefore the skin can't protect itself." The body's natural defense against too much sun is melanin, which makes skin dark, but too much exposure can cause the melanin to stain your skin, leaving age spots.  
Dr. Oz says wearing sunblock is important.

Sunblock shields your skin from the harmful ultraviolet rays. The Sun Protection Factor (SPF) rating you find on a sunblock bottle is based on how it blocks UVB rays, which cause sunburn. Dr. Oz says you should wear sunblock with an SPF of at least 15. Many sunblocks also block harmful UVA rays—which penetrate deep into your skin and cause aging and cancer. Dr. Oz says that the SPF refers to the protection from UVB rays—not UVA—and that the SPF number doesn't tell you if a sunblock protects you from both.

Dr. Oz says people with darker skin have already evolved a sort of natural SPF. Too much sun can break down important nutrients and other elements your body needs, and the melanin in darker skin protects from this loss. "Black-skinned individuals naturally adapted to protect themselves because they had too much sun," Dr. Oz says.

According to Dr. Oz, most sun damage occurs before you are 20 years old, so it is very important to protect children from too much sun. His rule of thumb is to make sure your shadow is bigger than you when you go outside because that means the sun is rising or setting, and to wear sunblock most of the time.
Dr. Oz and Oprah

Whenever I laugh, I pee. What can I do?

Most people aren't brave enough to ask about it, but 55-year-old Zondra is one of about 13 million Americans with this problem, Dr. Oz says. The bladder is located above the muscles in the bottom of your pelvis. Sometimes the muscles get "a little bit flabby" when you have a baby or as you age, making it harder to stop yourself from peeing. "Having a baby, by the way, does it a lot. Don't panic. It often gets better," Dr. Oz says.

If you have to run from the room when someone tells a joke, there is hope. Dr. Oz recommends Kegel exercises. He says that squeezing the muscles in your pelvis in order to firm them up can help prevent the problem. Also, you should drink less caffeine and use the bathroom more frequently, because the bladder leaks more when it's full. "Try to empty your bladder out if you're going into a social situation. Don't let people tickle you!" Dr. Oz says.
Dr. Oz and Oprah

Is douching a good way to stay clean?

Dr. Oz says the vagina is a "self-cleaning oven," and you shouldn't douche to stay clean. "You have your own bacteria in there. They're for you. You're supposed to have them there. When you wipe them out with a vinegar douche, then you're left with repopulating it with whatever happens to be nearby. It may not be what's best for you," he says.

Douching, Dr. Oz says, may even make you more likely to have some problems, such as ectopic pregnancies and infections that can cause infertility. "It's a big problem. That's why I don't think there's any really good reason to douche. Period," Dr. Oz says.

Keeping the vagina clean externally is important, and Dr. Oz says you should always wipe front to back to prevent urinary tract infections. And if you are worried about something in that area, you should go to a doctor and get treatment—Dr. Oz says that covering up problems with a douche won't solve anything.
Dr. Oz says if you get a Brazilian wax, make sure the wax isn't too hot.

Is it safe to have a Brazilian wax?

Dionne wants to know if it's safe to get a Brazilian wax, which is a bikini wax that takes "all the hair off from the front, the back, the bottom," Dr. Oz says.

Dr. Oz says it is "absolutely safe" to get a Brazilian wax, although your skin is fragile and prone to pimples for a short time afterward. There are some products you can put on your skin to prevent the pimples, he says.

If you are going to go Brazilian, Dr. Oz says to make sure the wax is clean—don't use wax that has been used on someone else. Also, check the wax to make sure it's not too hot.
Dr. Oz

Beyond Brazilian waxes, Dr. Oz has an even bigger question. "Do you ever sit back at night and think, 'Why do I have pubic hair?'"

Dr. Oz has two conclusions. "It prevents chafing. It actually lubricates the skin folds that are moving over each other," he says, but removing the hair doesn't usually lead to chapped skin. "The other more important reason is it's actually a bigger place for the pheromones to sit, the chemicals that you normally secrete that your loved one is actually liking."
Dr. Oz explains how Botox smoothes out wrinkles.

Is it safe to have Botox injections?

Carol's questions affects millions of people who have this cosmetic treatment every year to eliminate wrinkles on their faces. Dr. Oz says Botox comes from Clostridium botulinum, the bacterium that causes botulism. Small amounts can block the ability of nerves to stimulate muscles, he says. "So some of the lines between the eyes, the crow's feet, they're caused by muscles that keep scrunching back and forth, and they create a hinge in your skin," Dr. Oz says. "The Botox injection blocks that."

Dr. Oz says each injection works for about four months, and that it's not dangerous to have the injections sparingly. "But you've got to get someone who knows how to use it. Everybody who is a doctor in America can put Botox in you. But not everyone knows how to do it right," he says. "If you're going to have Botox injections, you should have them done by a plastic surgeon or a dermatologist."
Lindsay whitens her teeth every day.

Is it safe to bleach your teeth every day?

Lindsay says she is "obsessed" with bleaching her luminous smile, and she's done it every day for the last three years. Dr. Oz says when you bleach your teeth—the most common cosmetic procedure in the United States—hydrogen peroxide is used to remove stains and make your teeth appear whiter.

While teeth whitening is safe, Dr. Oz says there are some dangers. Some whitening products can take off your teeth's enamel and wear it so thin that you can actually see through your teeth. Your gums can also be damaged.

"You should limit yourself to a two-week treatment, or a really great idea is to get a dentist to do it and then follow it up with a week or two of doing it yourself, but doing it every day is a mistake," Dr. Oz says. Instead of whitening your teeth every day, you should floss.

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As a reminder, always consult your doctor for medical advice and treatment before starting any program.