There are no silly health questions, but some are gross

Maybe it's never crossed your mind to wonder whether sitting on a public toilet seat can give you something ghastly. Or if all-day heat-lamped rotisserie chickens are safe to eat. Or if getting your nose pierced is dangerous and-or reversible. Or a whole plethora of questions you'd hardly think to run by your best friend, no less your (gasp) doctor.

Fret not. Dr. Roshini Rajapaksa, Health magazine's medical editor and a physician who (among other things) specializes in women's health, has heard them all.

She's even heard some you probably never even dared to think about. She answers 240 such questions in her new book, "What the Yuck? The Freaky & Fabulous Truth About Your Body" (Oxmoor House; $19.95).

We pulled out five that don't make us blush — at least not too much.

Q: How bad is it really to borrow a friend's razor?

A: "Bad. Razors can pick up traces of blood and other bodily secretions, so you're essentially exposing yourself to your friend's blood and any infections or STDs lurking in her body (hepatitis B or C, herpes, HIV etc.)."

Q: Is it true my underwire bra will give me breast cancer?

A: "Not true! There was once a theory that underwire bras blocked the lymphatic drainage of the breast, causing an accumulation of toxins that could then lead to cancer. But lots of studies have looked at links between underwire bras and cancer and haven't found a problem. Plus, we know now that blocked lymphatic drainage doesn't lead to cancer."

Q: Sometimes when I take over-the-counter period medicine, I feel like my heart's beating out of my chest. Why does it affect me like that?

A: "Sometimes PMS or menstrual meds contain caffeine to help the symptoms of fatigue and bloating (caffeine is a diuretic, meaning it flushes out extra fluids) ... . If you're not a caffeine drinker or know you're sensitive to this stimulant, check out the label of any PMS meds before using them. Better yet, if you need the pain relief but don't want the caffeine, try a nonsteroidal anti-inflammatory drug like ibuprofen or naproxen."

Q: I recently read a celeb's blog about the importance of colon cleansing. How do I know if my colon needs cleansing?

A: "Trust me; it doesn't. As someone who looks inside people's colons every day — yep, that's my job! — I can tell you that for most people, the colon does a perfectly good job of eliminating waste."

Q: How do I know if I'm really depressed or just extra cranky?

A: "Depression is more than just feeling down or crabby ... . We don't know exactly what causes depression, but many people with the disorder have lower levels of neurotransmitters, or brain chemicals that are directly linked to mood ... . Just remember there's no reason to suffer. Depression is a real illness, and thankfully there are now good treatment options for it."