DEAR DR. DONOHUE: Please help me with some information on Coxsackie virus infection. This past summer was the second one in which my daughter (age 3) contracted this awful virus. She had high temperature (104) with sores on the mouth and throat. She could barely sleep and eating was a problem. It lasted about five days. Is this virus transmitted from public swimming pools? How contagious is it? Does one build up resistance to the virus? - P.A.C.

ANSWER: It's not easy to make predictions, but I'll bet your daughter is now immune to this virus and that you have seen the end of infections.Coxsackie viruses take up housekeeping in the digestive tracts of most humans, but only a relatively few become infected. It happens most often in children who have yet to develop resistance to the organism.

Two common Coxsackie infections are herpangina and hand-foot-mouth disease. With herpangina, blisters on a red base appear in the mouth along with high temperature. With hand-foot-mouth disease, similar mouth blisters appear, with the addition of scattered blisters on the backs of fingers and sometimes on the heel. Here, temperature does not rise. It appears from your description that your daughter had the herpangina type infection.

The Coxsackie virus is easily passed on from person to person, but as I said, infection is relatively rare. It's unusual to pick up the virus from a chlorinated public pool. Small unprotected home wading units are more likely havens for the virus. Parents should empty and clean these units frequently.

DEAR DR. DONOHUE: I came across a health article in which olive oil was on a list of foods to avoid on a low cholesterol diet. I have heard olive oil is OK. Please comment. - Mrs. M.L.

ANSWER: I rush to the defense of olive oil.

Olive oil, being a vegetable, has no cholesterol. And it is a mono-unsaturated fat, one of the good fats. So it's cleared on two important factors. In fact, people of the Mediterranean basin have traditionally used large amounts of olive oil, and they have only half the heart disease we do. That's not surprising, since mono-unsaturated fats actually lower cholesterol.

You can usually be guided nowadays by labels. The kinds of oil to use are those labeled polyunsaturated and mono-unsaturated. Avoid saturated fats. Note: All oils have calories and you must take that into account in any diet for weight control. See the cholesterol material. Write Dr. Donohue/No.5, Box 830, Gibbstown, NJ 08027-9909, enclosing a long, stamped, self-addressed envelope and $2.

DEAR DR. DONOHUE: My son, 25, is a liar. By this I mean he lies all the time about important and non-important things. He is a good son and really has no reason to lie like he does. We cannot understand his need to lie. Can this be a form of illness, and if so, where can he go for help? I am running out of patience and money (he is heavily in debt). - J.

ANSWER: Your son suffers from compulsion. The causes must be elicited by a mental health professional. Your family doctor can direct you to one.

FOR R.L. - The tissue removed in your prostate gland biopsy is replaced with scar tissue, as in any biopsy. The gland's function is not impaired with a biopsy.

DEAR DR. DONOHUE: In conversation with two other women, I noted variations in hormone names, dosages, etc. given for menopause. Please give me your opinion on the best treatment for menopause, the drug dosages, schedules, etc. - A.R.

ANSWER: Yours is a tall order. I can answer best by hop-scotching the subject with some general thoughts. As you might gather, there are honest differences of opinion among respected physicians on the best way to treat postmenopausal women with female hormones.

Most doctors opt for a combination of estrogen and progesterone, the estrogen given for 25 days, with progesterone added for 10 to 14 days. In this schedule, the remaining five days of the month are hormone free, and during this time, some women will have resumption of periods.

Other doctors opt for other schedules, and new ones are being examined for effectiveness. For example, use of both these hormones continuously with no hormone-free period is being tried to see if it is a better way to prevent osteoporosis (bone thinning) and heart disease with fewer side effects.

There are five different brands of estrogens with different strengths. But don't be confused by this. Their action is the same. Doses vary because women vary in needs. Higher doses of estrogen are given, for example, to women who have had their ovaries removed during their reproductive years (surgical menopause).

I guess what I am saying is that there is no best treatment for menopause. Uniform treatment is a goal toward which we are striving.

DEAR DR. DONOHUE: I have angina and have been taking a nitroglycerine tablet once a day for five years for it. Wouldn't I have developed an immunity to it by this time? - B.N.

ANSWER: A picky point perhaps, but the word isn't immunity, it's tolerance. I'll explain.

Sometimes when nitro drugs are used constantly in high doses and without any break, they can become less effective. A person can develop a tolerance to them. That is, his body has become inured to their action.

Now, this is not a dramatic thing usually. In fact, when it happens, effectiveness is restored after a very small vacation from the drug, a matter of, say 10 to 12 hours even. But since you are taking the drug only once every 24 hours, you should not encounter a tolerance problem.

How does one know when this tolerance has emerged? You judge by how you are faring. If you are starting to have signs of the heart pain the drug was preventing, you might be developing tolerance to it. If not, don't worry. Your other angina questions are addressed in the written material. To order, write Dr. Donohue/No.1, Box 830, Gibbstown, NJ 08027-9909, enclosing a long, stamped, self-addressed envelope and $2.

FOR A.L.B. - Having had an uncomplicated abortion, one where there was no subsequent infection, for example, you should not have problems conceiving again. As I have noted elsewhere, some women do not become pregnant for as long as 15 months after stopping birth control pills.

- FOR A COMPREHENSIVE discussion of how to cope with the change of life, send for a copy of Dr. Donohue's booklet No. 21, "Make Menopause Easier." Send your request to Dr. Donohue/No. 21, P.O. Box 830, Gibbstown, NJ 08027-9909. Enclose a long, self-addressed, stamped envelope and $2.00.

- Dr. Donohue welcomes reader mail but regrets that, due to the tremendous volume received daily, he is unable to answer individual letters. Readers' questions are incorporated in his column whenever possible.