Dear Dr. Donohue • We are grandparents in our early 80s with a 9-year-old grandson living with us. He is a bed-wetter, but in every other way normal, intelligent and healthy. We take him to the bathroom about three or four hours after bedtime, but often are too late. You addressed bed-wetting before, but a repeat would help us get through this difficult time. — S.B.

Answer • These remarks are not addressed to you, S.B. The tone in your letter indicates you handle a matter that is embarrassing to your grandson in a compassionate, humane way. Bed-wetting is something the child has no control over. Punishment and belittling are not productive.

At age 5, 7 percent of boys and 3 percent of girls wet the bed. By age 10, the percentages are 3 and 2. A significant number of children, therefore, outgrow the problem. Nerves that control bladder function may have matured or bladder capacity increased.

For your grandson, it helps to limit his fluid intake to one 8-ounce glass at the evening meal and then discourage any more drinking before bedtime if bedtime takes place about three hours later.

Have your grandson empty his bladder before going to bed. If you wake him about an hour earlier than you now do (two to three hours later), that could keep him dry through the rest of the night. Bladder training increases the size of his bladder. Ask him to delay in responding to the urge to urinate during the day. Allowing more urine to fill the bladder stretches it and increases the volume of urine it holds.

The next step is alarms that are activated by the first few drops of moisture. They either make a noise or cause a vibration that wakens the boy. Alarms have a success rate of 75 percent to 95 percent. You can find them at medical-supply stores.

Desmopressin is a medicine that slows urine production. Your grandson can use it if he's invited to sleep over at another's house. If you plan to use it, try it out at home a few times first to see how it works for him.

Dear Dr. Donohue • Is it possible to develop an allergy to milk later in life? I'm 45 and have drunk milk and eaten ice cream with enjoyment. Now they give me cramps and diarrhea. — D.M.

Answer • More likely than an allergy is a deficiency in lactase. It's an intestinal-tract enzyme that digests lactose, milk sugar. We're born with a good supply of lactase. It's a good thing we are, because milk is the chief infant nutrition.

With age, the intestine loses much of the enzyme. Blacks develop the insufficiency more than whites do, but all ethnic groups have a loss of the enzyme with age. Doctors can test for lactase deficiency.

Write Dr. Donohue at P.O. Box 536475, Orlando, Fla. 32853-6475.