Antibiotics are everywhere and can be purchased with very little trouble, either at some pet stores (where they're labeled for fish) or through Internet sources. Is it a good idea to keep some on hand in case your pet gets sick? In a word, "no."

Antibiotics are one of the outstanding contributions of modern medicine and have saved countless lives of both the human and animal variety. But we have become so comfortable with these medicines and their frequent usage that we sometimes forget they are powerful drugs that should be used with care.

And yet, some pet lovers respond to any sign of illness by dosing -- and often overdosing -- their animals with antibiotics. But this course of action is a bad idea for several reasons.

First, not all antibiotics are the same. They each have their target bacteria, and they may little affect any bacteria they're not designed to combat as well as bacteria that are resistant to them. And if your pet has a viral or fungal infection, an antibiotic will not help and may make matters worse. Second, the regular use of antibiotics may hurt your pet's immune system and may lead to the development of antibiotic-resistant strains of bacteria that will be hard to stamp out even with the "right" medication. And finally, the improper use or overuse of antibiotics presents an environmental hazard. When your pet is sick, your time and money would be better spent getting an accurate diagnosis and targeted treatment from an experienced veterinarian.