Common side effects of antibiotics include upset stomach, diarrhea, and, in women, vaginal yeast infections. Some side effects are more severe and, depending on the antibiotic, may impair the function of the kidneys, liver, bone marrow, or other organs.
Some people who take antibiotics, especially cephalosporins, clindamycin or fluoroquinolones, develop colitis, an inflammation of the large intestine. This type of colitis results from a toxin produced by the bacteria Clostridium difficile, which is resistant to many antibiotics and which grows in the intestines unchecked when other normal bacteria in the intestine are killed by the antibiotics
Antibiotics can also cause allergic reactions. Mild allergic reactions consist of an itchy rash or slight wheezing. Severe allergic reactions (anaphylaxis) can be life-threatening and usually include swelling of the throat, inability to breathe, and low blood pressure.
Many people tell their doctor that they are allergic to an antibiotic when they have only experienced side effects that are not allergy-related. The distinction is important because people who are allergic to an antibiotic should not be given that drug or an antibiotic closely related to it. However, people who have experienced minor side effects can usually take related drugs or even continue taking the same one. Doctors can determine the significance of any unpleasant reaction people have to an antibiotic.
