Zinc gluconate is available without prescription at some pharmacies and health food stores. But before trying it, talk it over with your doctor. Then, if you decide to go ahead, do not exceed the dose Eby and his colleagues used in Texas and do not take the tablets for more than a week.

A recent study at Memorial University in Newfoundland found preliminary evidence suggesting that long-term use of 300 milligrams of zinc a day -- about the same zinc dose that Eby and Halcomb administered -- may have adverse effects on blood cholesterol and the body's immune system. Besides, prophylactic use of zinc -- taking it to prevent the onset of colds -- has been found not to work.

Eby warns, too, that zinc gluconate can cause oral irritation. This is most likely to happen if you fall asleep with a tablet in your mouth. Also a good idea -- to prevent queasiness -- is to avoid taking the tablets on an empty stomach and to nibble on soda crackers if your stomach protests.

Finally, any zinc gluconate you buy should contain only zinc gluconate. Some formulations are enriched with even worse-tasting ingredients, such as liver extract, that won't do anything for a cold.