A weak hydrogen peroxide positive test may occur when the vagina is infected with bacterial colonies due to: 1) excessive local cleansing or lack of hygiene in daily life; 2) frequent sexual intercourse or prolonged vaginal drug use; 3) dysbiosis of the vaginal flora due to an excessive reduction of lactobacilli; 4) a mild increase in the concentration of hydrogen peroxide in the vagina. A mild increase in the concentration of hydrogen peroxide in the vagina may also give a weak positive result. The patient’s body may become resistant to metronidazole when the symptoms recur.