Dear Dr. Donohue — I am a 32-year-old woman, married with two children. For this entire year, I have not been myself. I have had loose stools at least twice a day, and have lost 20 pounds without trying. Finally, my husband insisted I see a doctor. I did, and that doctor sent me to a gastroenterologist, who diagnosed celiac disease. I have just started a gluten-free diet. Can you tell me more about it?— K.M.

Answer — When celiac disease was discussed in medical school, my reaction was: Here comes another illness I'll never see. I was very wrong. Celiac disease is quite common. Estimates say that one in 113 people has it. In a population of more than 300 million, that amounts to a lot of people.

It's an illness brought on by the immune system, whose attack on the small intestine makes gluten trigger diarrhea, weight loss and many other conditions brought about because of poor absorption of things like iron and calcium. The presenting problem with some celiac patients is not digestive symptoms, but is osteoporosis because of calcium deficiency or anemia because of iron deficiency. The celiac diagnosis is made by finding special antibodies in the blood and by a biopsy of the small intestine.

Strict avoidance of gluten — a protein found in wheat, barley and rye — usually reverses all the signs and symptoms of this illness. For some, oats can be a problem too. Once a celiac patient is free of gluten exposure, symptoms usually remit in weeks to months.

You need help mastering the gluten-free diet. A dietitian can instruct you on what you can and cannot eat and can tell you hidden sources of gluten. Corn, rice, legumes, nuts, potatoes, soy and tapioca are substitutes for the banned grains. The Celiac Disease Foundation has a website at www.celiac.org, and the phone number is 1-818-990-2354.

Dear Dr. Donohue — I was recently hospitalized for swelling and redness of my legs, with an itchy rash and painful joints. I was taking two diuretics at that time, Bumex and Zaroxolyn. The doctors took me off all medicines. They were going to start a small dose of Bumex again when the doctor in charge asked if I am allergic to sulfa drugs. I said, "Yes." He said, "Maybe we have found the cause." Many diuretics are related to sulfa. I stayed off the medicines, and my symptoms started to clear. — F.H.

Answer: Bumex (bumetanide) and Zaroxolyn (metolazone) have a chemical structure similar to sulfa. Many other diuretics have the same structure. They can cause an allergic reaction for people who have a sulfa allergy. They also can cause a similar reaction in people without a sulfa allergy.

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