How do antibiotics work?

Question

How exactly do antibiotics help your body? What are the positive and negative effects?

Answer 1

Antibiotics are drugs that selectively inhibit pathogenic microorganisms (bacteria, viruses, parasites, etc) typically by suppressing a necessary metabolic function (which is incompatible with growth for the microorganism), or by directly damaging the microorganism. An example is penicillin, which prevents formation of the bacterial cell-wall, producing a situation where the bacteria can no longer osmotically-regulate itself, and essentially explodes.

They help you by eradicating infections by the microorganisms which may in some cases be otherwise life-threatening. For example, Bacillus anthracis infection (Anthrax) is virtually fatal without antibiotic treatment.

Negative effects include unintentional destruction of "good" flora that normally inhabit some regions of the body, like the colon, which might allow other nastier bacteria to grow in their place. Other potential negative effects are allergic reactions, toxicities, etc.

Answer 2

An antibiotic is a drug that kills or prevents the growth of bacteria.

Possible side effects are varied, and range from fever and nausea to major allergic reactions. One of the more common side effects is diarrhea. Other side effects can result from interaction with other drugs.