You arrive at work one morning to discover an e-mail warning that tampons—and even worse, your favorite antiperspirant—contain various toxins and have been implicated as a cause of cancer. Although overstated and generally incorrect, this misinformation is benign compared with some of the myths that have historically surrounded women's bodies and health.

Thank goodness we know more about reproduction, for example, than did our medieval ancestors, who staunchly believed that the sex of their progeny was determined by the mother. Before medical science discovered that a baby's sex was determined by the father, not the mother, there's no telling how many queens lost their heads for failing to produce a male heir!

Experts warn myths can be especially dangerous if they prevent women, and even the medical community, from addressing true health risks. Below are a few such myths.

Myth: Breast cancer is the leading cause of death among women.

Fact: Heart attacks, strokes and other cardiovascular diseases claim the lives of more than 500,000 women each year compared to 43,000 for breast cancer. But Dale Mintz, MA, formerly with the American Heart Association and now director of Hadassah's National Department of Women's Health, says that women fear breast cancer more than heart disease.

"Historically—although this is usually no longer the case—women who went to a doctor with chest pains were given Valium or antidepressants for anxiety, whereas men would be checked immediately for heart disease," Mintz explains. "And women don't take care of themselves as well as they do their partners and children. They get to the doctor later, when their prognosis may not be as good."

Myth: Breast cancer is the leading cause of cancer deaths.

Fact: Lung cancer kills about 67,000 women annually, half again as many as breast cancer. "We're learning that women are at higher risk of developing lung cancer even if they smoke less than men," says Sherry Marts, PhD, scientific director of the Society for Women's Health Research. "And when women get lung cancer, it's a more invasive form that's harder to treat. One of the best things that women can do to prevent lung cancer it is not to smoke—EVER."

Myth: Getting hit in the breast can cause breast cancer.

Fact: Emphatically NO! This old myth persists because occasionally an injury will cause a benign lump in the breast, which usually disappears in a few weeks. When Mintz makes breast cancer awareness presentations to high school girls, it's not unusual for a girl to ask if it's safe to play sports even though they might get cancer from being hit in the breast. This is one of those myths that's dangerous because it undermines a healthful behavior. "We want them to play sports because exercise is so important to their health," she says.

Myth: Prevention of osteoporosis begins with menopause.

Fact: While the loss of bone mass that affects one out of two women typically begins after menopause, prevention begins much earlier with health habits that promote bone strength. The National Osteoporosis Foundation (NOF) advocates a diet rich in calcium and vitamin D, cautions against smoking and excessive use of ]]>alcohol]]> , and has launched the Step On It America! campaign to promote weight-bearing exercise.

]]>Walking]]> , dancing, playing ]]>tennis]]> , and ]]>lifting weights]]> are weight-bearing exercises; ]]>swimming]]> and bicycling, which are excellent for cardiovascular health, do not strengthen bones. An exercise program that combines both weight-bearing and cardiovascular activities will benefit both your bones and your heart.

Myth: A nursing mother can't get pregnant.

Fact: This is an old wives' tale that has at least a kernel of truth in it, says Barry Jacobson, MD, chairman of the Obstetrics and Gynecology Department at Delaware County Memorial Hospital in Pennsylvania and adviser to the National Women's Health Resource Center. The truth is that breast-feeding will delay ovulation. However, although a nursing mother does not ovulate in the early months of breast-feeding, she may ovulate in later months. Hence, a form of pregnancy prevention should be resumed as the months go on. It is best to consult your health practitioner about this issue.

Myth: Treatments tested on men are appropriate for women.

Fact: We don't know. Recognizing the gaps in what is known about women's health issues, the National Institutes of Health (NIH) established the Office of Research on Women's Health (ORWH) in 1990. This group has worked to find those gaps and to assure inclusion of women and minorities in clinical studies funded by the various institutes and centers that make up the NIH.

Myth: A "fishy" vaginal odor is normal.

Fact: The odor may be the result of bacterial vaginitis (BV), a condition more common and more serious than yeast infections.

According to the 3M National Vaginitis Association (NVA), if untreated, BV can lead to infertility or pregnancy complications, including pre-term birth. Symptoms of BV include a discharge, fishy odor and perhaps itching, which women often mistake for a yeast infection. "It's alarming when you consider the number of women who incorrectly self-diagnose their vaginal infections," says Daron Ferris, MD, of the Department of Family Practice, Medical College of Georgia. "Because there is a lack of information, these women may take matters into their own hands, use an over-the-counter antifungal and incorrectly treat what may be a serious vaginal infection."

Myth: You can get a sexually transmitted disease (STD) from toilet seats.

Fact: "It's OK to sit down," reports Dr. Marts. "Most organisms that cause STDs will not survive for long on a toilet seat." She adds that viruses such as those that cause herpes and hepatitis can survive, but a woman would have to make genital contact with the seat to become infected. "I think this myth dates from a time when it wasn't so much about microbes as it was about vermin, like fleas and body lice," says Dr. Marts.

What about the tampon and antiperspirant rumors?

Do antiperspirants, as the e-mail warns, prevent the release of toxins that can back up and cause breast cancer? All the leading breast cancer organizations, including the Susan G. Komen Breast Cancer Foundation, refute this myth, pointing out that sweat doesn't even contain toxins and that sweat blocked by antiperspirants is excreted elsewhere.

Another email says that leading tampons contain dioxin, a known carcinogen, and therefore you should use all-natural tampons. "There's not a lot of difference between natural tampons and the kind you buy in the grocery store except the cost," says Dr. Marts. She says that dioxins, some more dangerous than others, are found everywhere in the environment, including our bodies, drinking water and food. "[Researchers] are able to detect it now at .02 parts per trillion, and they're not able to detect any in tampons at that level."

Dr. Marts believes the danger of such email warnings is that they scare people who fear they've been damaging their bodies unwittingly for years. "If you read something in an email, don't believe it unless you can confirm it with a physician or a reputable web site," she says. See the resources below for some reputable websites with women's health information.