Why is it that when a person vomits, it causes others to vomit — even when they don't have an illness causing it? Is this something triggered by the brain or is it something that happens by reflex (survival instinct) for someone to vomit since, perhaps, what the first person was eating may affect the second who vomits as well?

A couple of months ago I developed a hard, bony growth on my instep. I noticed that the top of my foot was hurting, and when I took my shoe off, there was a red lump the size of a quarter (it's not red all the time, just from rubbing against the shoe). A friend of mine who is a nurse said that it's probably a ganglion cyst and the best thing to do would be to, and I quote, "hit it with something really hard," like a dictionary, or a hammer. It should break up immediately, she told me. She hasn't seen it, by the way — this was over the phone.

I'm surprised that she thinks it's a cyst, because it's awfully hard — I would have just thought that it was a bone spur. What do you think? And is smacking a cyst with a dictionary really the way to go?

As an avid contact wearer, I use saline solution to rinse my contacts daily before each use. Recently, a friend told me that many commercial saline solutions contain preservatives, which could affect the overall health of my eye. Is this something I should be concerned about? The saline I use has always felt comfortable so I never thought it could pose a problem.

Does a person's menstrual cycle regulate her bowels in any way? I have had some problems. The week before I get my period, I have loose bowels and the week afterwards I am quite constipated. Is this normal? Is there anything I can do?

I have had Crohn's disease for 16 years and am in remission right now. Recently my boyfriend and I have been toying with the idea of anal sex, but I'm concerned about it given my health issues. I have a lot of thickening of the terminal ileum walls and worry that the "trauma" of anal sex could set off a flare up and be painful because of the narrowing. Any thoughts? I'm way too embarrassed to discuss this with my male doctor. Thanks!

I just found out that a friend requires a kidney transplant. I've heard that we are all equipped with two kidneys and can live with just one. How do I find out if I can donate a kidney? What's involved in a kidney donation? Thanks!

What natural food or herb can help soothe stomach ulcers?

I read that disposable contact lenses are actually worse for your eyes than the normal one-year ones because they allow less oxygen to go to your eyes, and the only advantage is that there are less cleansing problems. Also, it is claimed that inadequate oxygen to your eyes (possibly caused by prolonged wearing of contact lenses) leads to a condition when extra blood vessels sprout around the iris, which leads to sight problems at old age. Is that true?

I am very concerned because I normally wear (one-year) contact lenses from 8am to 8pm, and maybe to 12am during reading periods. I don't feel very comfortable with glasses because they give distorted visions and fatigue. I thought switching to disposable contact lenses would do my eyes good. My current lenses contain 38 percent water. Is this good enough?

The muscles in my back become extremely tense/tight throughout the term as I am cramped down studying all the time. What should I do?

1) I'm a college student and I've heard in the media that meningitis vaccine shots are recommended. How do I get more information and a shot?

2) As a parent of a college freshman this fall, I was concerned about the increasing publicity that Meningitis has received recently over the networks. Since the population most likely to be infected includes young adults living in close quarters, do you recommend vaccination and where is it available?