Q: Sometimes while I'm eating, my face and neck start perspiring, and my hair gets wet. Is this an allergic reaction to my food?

A: It's a reaction, but not an allergic one.

You're having what's known as gustatory sweating, meaning sweating triggered by certain foods. "Gustatory" comes from the Latin word for taste.

Foods, particularly spicy ones, can stimulate nerves in the mouth that are connected to sweat glands around your face. Interestingly enough, once you've had this experience a few times with certain foods, you can experience a reflex sweating just thinking about eating that food.

Q: I'm 21 and I have been smoking since I was 9. I hate smoking. I hate running out at all times to buy cigarettes. I hate the smell, I hate the burns, and most of all I hate the power cigarettes have over me. I'm also very scared of the consequences I'll face if I don't quit.

I also love smoking. I love smoking after that big heavy meal. I love the security they offer when I'm depressed, sad, angry or bored.

I've tried to quit through stop smoking courses offered by hospitals, but I always won -- I didn't quit. I've always thought I'd quit before trying to bear children, maybe when I'm 30, but I don't know.

This is where you can help. I'd like to know more about quitting smoking through hypnosis and acupuncture. How successful are these techniques? How much do they cost? How do I find someone who is reputable?

A: It sounds like you don't really want to stop smoking. You have a lot of ambivalence about quitting, but the tip-off is that you side with the part of you that somehow feels victorious by flunking a stop-smoking course.

Quitting smoking can be extremely difficult. About half of smokers are genuinely addicted to smoking, a habit many experts say is harder to kick than heroin addiction. So before you set out to stop smoking, you really need to be committed to quitting.

There is no single way to stop, though most people who quit do so by themselves, usually going "cold turkey." Methods of quitting, including nicotine gum, group courses, individual counseling and hypnosis, have success rates ranging from 20 to 40 percent. Acupuncture isn't as well-tested a method, but I would guess it wouldn't be any more effective than traditional techniques.

Depending on the length of treatment, hypnosis and acupuncture will probably cost between $50 and $200. You can look in the Yellow Pages to find hypnotists or acupuncturists who treat smokers. I'd recommend asking what their success rate is in helping smokers quit for at least one year. If it's 40 percent or better, that's pretty good. You might also take a look at the book "How to Stop Smoking Through Self-Hypnosis" by Leslie LeCron (Wilshire Press, $3).

In the end, your motivation to quit is more important than the method you choose.

For more information on stop-smoking techniques, write for the booklet "Clearing the Air" from the Office of Cancer Communications, National Cancer Institute, NIH, Bethesda, Md. 20892; 800-4-CANCER.

Q: I had prostate "skimming" surgery in 1979. When will I have to undergo surgery again? I've heard you need to have it done every seven years, or thereabouts. Also, does having an enlarged prostate cause impotence? Does prostate surgery? Or could it be my 70 years of age?

A: You had what doctors call a TURP -- short for transurethral resection of the prostate. This means removing some of an enlarged prostate gland through a small tube inserted through the urethra (urine channel) in the penis. Many people think of this as a kind of Roto-Rooter operation for your urinary plumbing, and that's not far from the truth.

Just because you needed the operation once doesn't mean you'll need to have it again. In fact, most men won't need further surgery for the same problem.

An enlarged prostate in itself doesn't cause impotence. The main symptoms of an enlarged prostate are difficulty in urinating, dribbling, having a weak urine flow, and feeling strong or frequent urges to urinate, sometimes without being able to go.

Prostate enlargement is very common, and affects many men past the age of 60. If you live long enough, you're bound to have some difficulty with this problem. Besides being a nuisance, it can lead to a urinary tract infection and complete blockage of your urine flow.

The kind of prostate surgery you had rarely causes impotence. Men with prostate cancer who have their prostate removed through an incision in their abdomen are more likely to become impotent. But one side effect of TURPs is something called retrograde ejaculation, meaning that during orgasm semen is discharged into the bladder instead of out the penis. Aside from making you unable to have children, this isn't harmful and doesn't interfere with your ability to have an orgasm.

Although sexual activity tends to lessen with age, I don't advise blaming your age alone as a cause of impotence without discussing this concern with your doctor. Other causes might be the culprit, ranging from doubts about your sexual function after prostate surgery, to side effects of certain medicines, or medical problems like diabetes, hardening of the arteries or alcohol abuse.