DEAR DR. DONOHUE: I have some questions on flu and the flu vaccine. I don’t intend to get the vaccine. I have had the flu a couple of times, and all it amounted to was a day of diarrhea. I don’t need a vaccine for that. I also have heard that the vaccine can paralyze you. If I should change my mind, when is the best time to get it? How long does it last? — R.T.

ANSWER: Flu, influenza, is a serious illness. Around 36,000 Americans die from it every year. It’s a respiratory illness, not a digestive-tract illness. It comes on suddenly and causes a cough with a high temperature. Muscles ache. The symptoms are much more dramatic than those of the common cold. Sick people take to their beds because they feel so terrible. Diarrhea is not a common sign of flu. It’s true that the swine flu might cause loose stools for a day or two, but the other flu viruses do not home in on the digestive tract. “Intestinal flu” is a misnomer.

The flu vaccine, while not perfect, does work well for most people. If a vaccinated person catches the flu, symptoms are less serious and less prolonged. Reactions to the vaccine aren’t common, and they’re mostly minor — like swelling at the injection site or a day or so of muscle discomfort.

In the late 1970s, there was an outbreak of a variant form of flu; some people, after getting the vaccine, developed Guillain-Barre syndrome, an illness that can cause temporary paralysis. Whether there was a cause-and-effect relation to the vaccine wasn’t established.

It takes two weeks for a person to develop protective antibodies against the flu after receiving the vaccine. The flu season lasts from November to May. Anytime during that period is the time to get the vaccine, but the earlier the better. Protection lasts through the entire season.

DEAR DR. DONOHUE: I have been talking in my sleep for 10 years. It bothers some people. How do you get it? I also talk back to people when I’m sleeping. Is it true that when you talk in your sleep and people ask questions about anything you’ve done, you cannot tell a lie? — S.M.

ANSWER: Sleep talking is a common occurrence. The sleeper is unaware of what he or she says. Sometimes the talking is pure gibberish, but other times it makes sense. It’s not a sign of a physical or mental problem. No treatment is necessary. What makes it happen isn’t clearly understood.

If people ask a sleep talker a question, most often, if not always, the talker doesn’t give any answer. Are you thinking of spy books and movies where a captured person is given a truth serum by an enemy to extract valuable information? That doesn’t happen. It never did. Everything a sleep talker says isn’t necessarily the truth.

DEAR DR. DONOHUE: Through the years I have read your column, I don’t remember reading any comments on hydroceles. I am a 70-year-old man and was told I had one by a urologist about two years ago. It has started to become uncomfortable — not painful, just uncomfortable.

An Internet search revealed that after an outpatient procedure, one can expect a hydrocele to recur.

My question is: If I have the procedure, how long would it take to become uncomfortable again and require another procedure? — B.G.

ANSWER: A hydrocele is a collection of fluid around the testicle. It’s more apt to happen to men older than 40. Unless it is large and uncomfortable, it can be left alone.

Hydroceles make a doctor think of tumors of the testes, infections or trauma. Most of the time, none of these things is present. When they do happen, the man is usually one of a younger age.

Draining the hydrocele with a needle and syringe is followed by a recurrence quickly. Surgical removal almost always puts an end to the problem permanently.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Readers may also order health newsletters from www.rbmamall.com.