Q: We have an intelligent, affectionate, shy and somewhat insecure 2 1/2-year-old. He's not toilet-trained yet and that is our problem. Well-meaning friends and relatives seem to think children should be trained at 2.

We have tried to train our child but he takes no interest. He won't even try to sit on the toilet. We tell him what a big boy he will be when he is out of diapers, but we don't really force the issue. Is this the right way?

A: To you and the many other parents who ask if children should be trained at 18 months or 2 years or 2 1/2: The answer is, Heavens no. Some children -- especially those with older brothers and sisters -- train themselves before age 2, but most are 3 or even 3 1/2 before they're ready -- especially boys.

You can't train a child until his central nervous system is mature enough for him to know when he has to go, physically mature enough for him to control specific internal muscles -- and until he's psychologically mature enough to care. You'll know he's ready when he's dry for about two hours at a time and perhaps wakes up dry after his nap and even in the morning. Above all, he'll be interested in the subject.

And so, of course, will you.

That's when you say, "Okay, kiddo. You're a big boy now."

When the time comes, it will mean a week at home for both of you so accidents are less likely, compliments and kisses when the child is successful, and a matter-of-fact clean-up, by both of you, when he's not.

He'll need a potty chair that sits on the floor -- because he might be afraid he'll go down with the flush -- an array of nifty new underpants, clothes he can slide out of quickly, and the prospect of a wonderful present when he's trained, like a tricycle or Big Wheel, in honor of his new grown-upness. And if you think this is bribery, you're right. Eventually, almost everything has its place in parenthood.

Q: I have a 5-year-old daughter who wets the bed. I kept her in diapers at night until recently when she developed a bad rash. The last few weeks, we have tried waking her when we go to bed, but it's difficult to wake her and she still wets later in the night. We tried an alarm clock set at 2 or 3 a.m., but she just turns it off and goes back to sleep. It seems that she just sleeps very soundly.

She is a healthy, happy, well-adjusted child -- very good-natured and easygoing, doing well in kindergarten. She trained herself to use the potty at about 21 months, with very little encouragement.

I don't want to cause more problems by trying to solve something if she will outgrow it, as I did. I was 5 before I was dry at night, and my husband had a problem with bedwetting into his pre-teen years. My older daughter slept dry most nights by age 3, with occasional accidents until about 6 or 7.

Should we wait or try other alternatives?

A: The bedwetting of a 5-year-old may seem like a psychological problem, but this is seldom the case.

Today's forward-thinking doctors usually recognize it as an allergy to something the child smells, touches or eats, especially if she sleeps deeply, has a history of bedwetting in the family or craves certain foods -- all signs of allergy.

Allergic reactions vary from food to food and from person to person, depending on what part of the body has been sensitized. Just as chocolate may make the air tubes of an asthmatic go into a spasm, grape juice can do the same to the sphincter muscles and cause bedwetting -- at least until the pelvic cavity expands in the pre-teens and gives the bladder more space.

Dr. Doris Rapp, a pediatric allergist from Buffalo, N. Y., finds that milk and juices -- especially pineapple juice -- are among the most likely causes, while other doctors report that foods such as corn, wheat, pork and eggs can be the trigger.

If food is the cause, you can find out with a five-day elimination diet.

To test your daughter, give her the foods she seldom eats instead of those she likes best and eats most -- substituting turkey for chicken, for instance, mangoes for apples, potato chips for popcorn -- and avoid anything containing corn, wheat, chocolate, eggs, milk, sugar, orange, dyes and preservatives. If a food is the problem, and it's among those you've dropped, she should stop wetting the bed by the fifth day.

You then return one food each day and at night you find out if it is the culprit.

Dr. Rapp's Allergies and the Hyperactive Child (Cornerstone, $4.95) describes the test in more detail. Coping With Your Allergies by Natalie Golos and Frances Golos Goldbitz (Simon and Schuster, $17.25) will help you live with a new diet.

If your home test is negative, try a urologist; there may be a minor valve problem. If that doesn't work, wait until your child is 6 and more motivated to stay dry before you consider other solutions. A moisture-sensitive pad often conditions a child rather quickly, but it may be embarrassing and cause her to sleep lightly, and the drugs given to prevent bedwetting may make her lethargic.

It's better to solve the problem than treat the symptom.

Questions may be sent to Family Almanac, P.O. Box 15310, Washington, D.C. 20003.