DEAR DR. DONOHUE: We have a 12-year-old grandson who is a bed-wetter. His mother took him to the doctor, and the doctor prescribed medicine. My daughter looked up the drug and found that it has many side effects, so she would like to keep him off it. We found many different devices on the Internet. We write to you for your recommendations. – C.G.

ANSWER: The most important advice I can give you about bed-wetting is to stay calm about it and have your daughter and grandson also stay calm about it. Equally important is neither to be punitive toward the child nor to humiliate him in any way. Bed-wetting is not voluntary.

Most children attain nighttime bladder control around age 5. At that age, 7 percent of boys and 3 percent of girls wet the bed. At 10, the percentage drops to 3 for boys and 2 for girls. By 18, only 1 percent of boys still wet the bed, and it is rare for girls of that age to do so.

Theories explaining bed-wetting abound. One says that bed-wetting children’s bladders have not expanded enough to hold all the urine produced during sleep. Another theory is a diminished production of a hormone that slows urine production during the night. Third, some children might lose control because they are deep sleepers and impervious to the signals coming from a full bladder.

Your grandson should go to the bathroom before going to bed. His fluid intake in the late afternoon and evening should be much less than it is at other times of the day. If the boy agrees to this, he can set an alarm clock to go off two to three hours after he goes to bed so that he can get up to empty his bladder.

A bed-wetting alarm system helps many bed-wetters gain control. A few drops of moisture on a pad placed under the child activate an alarm that wakens him so he can then get to the bathroom to empty his bladder completely. The child should have the deciding vote to use or not use such devices..

In the past, readers have taken me to task for not mentioning the possibility of food allergies being a cause of bed-wetting, and they often point to milk as being the greatest food cause. I don’t know about the reliability of this information, but I’ll bow to readers’ experience.

DEAR DR. DONOHUE: I developed blood clots in my leg and lungs. I was put on Coumadin (warfarin). My dose was adjusted twice. I understand that losing my hair is a side effect, but I don’t understand what Coumadin is supposed to do. It doesn’t appear to be working, so why can’t I quit? – K.P.

ANSWER: It is working: You haven’t developed any more clots. People who have had clots are at high risk of developing more clots in the months following the first episode. Coumadin has stopped clots from forming again.

After a first experience with clots, people take Coumadin for a number of months, often six. If the clots were severe or if no remedial cause can be found for them, then there is a possibility of having to stay on blood thinners for protracted periods, sometimes for life.

Hair loss is listed as a side effect of Coumadin. It’s a rare side effect. The number of people who take Coumadin is very large. The number of people who have experienced hair loss as a side effect of Coumadin is very small. If your hair loss really results from Coumadin, it’s a price you have to pay for removing a grave danger to your life.