Metronidazole is used to treat a wide variety of infections caused by anaerobic bacteria and micro-organisms called protozoa. These types of organisms often cause infections in areas of the body such as the gums, pelvic cavity and abdomen because they do not need oxygen to grow and multiply. It is commonly prescribed to treat an infection called bacterial vaginosis. It is also prescribed before gynaecological surgery and surgery on the intestines, to prevent infection from developing. Metronidazole can safely be taken by people who are allergic to penicillin.