Q. Your article on the hyperactive child was of great interest to me.

We had a boy exactly like the little fellow in your article--the one who was so hyperactive he even would climb into the refrigerator. For 10 years our son never sat, so we never did either. I even had to feed him on the run.

We tried most of the neurologists in the Washington area for five years, but no one could do anything for him. In fact, most couldn't stand him. My husband would keep him in the waiting rooms while I explained his problems, then the doctors would check him over quickly and get rid of him fast.

We were desperate as we had three older boys. Finally a friend hand-carried a brief history to Mayo Clinic, which in turn suggested the Medical College of Virginia in Richmond.

They gave him a complete check-up (it took a week), monitored him for five years and then sent him to Mayo when he was 10. He is 18 now, not hyperactive and a great boy to enjoy.

The diet did not work for my son, but I saw a lot of children at M.C.V. who were helped by it.

A. There's a good lesson here.

One problem can have many symptoms and many causes. And the more obscure it is, the more parents must pursue it, monitoring their child like the precious prize he is. This often means trying one technique after another, or doctor after doctor, until something finally works.

One of the main problems with hyperactivity is deciding whether it's a physical or an emotional problem, or if it exists at all. Physicist Norman Walker of Gaithersburg offers hope with the modification and improvement of a device he developed in the '60s--used both in this country and Britain--to identify fighter pilots who best can tolerate stress. Walker claims his Pan-ZITA can document hyperactivity, hypoactivity, attention-deficit disorder and vision conflict (when the eyes don't synchronize exactly).

The machine, already tested on more than 2,000 kids, will be studied more at Georgetown Hospital and other institutions. It takes a child about 10 minutes, says Walker, to play its video-type games and produce computerized results that help doctors decide whether to prescribe drugs, a diet or psychotherapy and to track the child to see if treatment is working.

The machine has been used in Germany to see if hyperactivity is caused by the phosphates used in junk food, hot dogs and sausages, and in England, where the problem has been linked to a deficiency of prostaglandin E1, a hormone-like substance.

Whatever the cause, hyperactivity in a child greatly damages the egos of his parents (and himself). It also warps the whole fabric of the family, particularly if there are other children. Relationships often grow askew under stress.

For parents who are faced with this dilemma, or who simply feel they should get along better with their children, there is a good book called The Ozer Method, by Mark N. Ozer, M.D.--a Washington neurologist--and Jean E. Collins (Morrow, $12.50). Its simple techniques, designed to fortify the whole family, should help improve any relationship.

Many parents already have found great help from the Association for Children With Learning Disabilities: Hyperactivity often goes hand-in-hand with learning disabilities. The association holds its national conference Feb. 16-19 at the Washington Hilton. For more information on the association, write: 4156 Library Rd., Pittsburgh 15234.

Q. My daughter, who just turned 5, is a bedwetter, even though we follow all of the necessary precautions.

She is a very happy and outgoing child and at the same time very strong-willed and determined. She seems to be very well-adjusted and is doing quite well in kindergarten. She loves everything about life and never seems to be bothered by any new situations or experiences.

Should we be concerned with her bedwetting? Is it something she will outgrow? I know some people say bedwetting is somewhat hereditary, but our daughter was adopted as an infant so we don't know if that is part of her past.

I might add that Laura is a very heavy sleeper.

A. Although pyschotherapy has done a great deal of good, the Freudian fall-out has made parents look for an emotional problem behind every behavioral bush.

Your letter is a good example of today's thinking. Even though your little girl is as happy as a pig in clover, you're trained to consider her personality instead of her body.

Several years ago Dr. James C. Breneman, head of the food allergy committee of the American College of Allergists, reported that an allergic reaction to a food irritates the bladder and causes the lining to swell and become inelastic, so it cannot hold urine. The spincter muscle also swells so it won't shut tight. According to Breneman, this theory isn't even controversial any more.

A child with this problem sleeps too heavily to wake on her own. This is typical of the allergic child (as are dark circles or puffiness around the eyes, breathing through the mouth and dozens of other symptoms).

The foods that usually cause allergies are the most common ones. Breneman reports that milk is the biggest offender and then eggs, wheat, corn and pork.

Even if you didn't change your child's diet, she has a 98 percent chance of outgrowing the problem around 12 or 13 (or 15, if she were a boy). This is because the pelvic structure enlarges at puberty and the bladder capacity almost doubles.

To understand the problem better, you'll learn a lot from a simply written book, Tracking Down Hidden Food Allergy by William G. Crook, M.D. (Professional Books). The book also is illustrated simply, so you can read it to your daughter. Cooperation will be easier if she can understand the problem.

Dr. Crook also has written Can Your Child Read? Is He Hyperactive? (Each book $7, Box 3494, Jackson, Tenn. 38301.)