The fungus species Candida albicans most commonly causes vaginal yeast infection. Recurrent vaginal yeast infection can be caused due to less common species of Candida, such as Candida glabrata or Candida krusei. Yeast is found on normal human skin and areas which remain moist such as the mouth and vagina but it does not cause disease or symptoms. Studies indicate that about 20%-50% of healthy women have candida in the vaginal area. Infection is caused due to increase in the number of Candida in the vagina relative to the number of good bacteria under certain favourable conditions such as:
After antibiotic therapy: It kills not only bad bacteria, but also good bacteria. The good bacteria help to prevent the overgrowth of yeast. Decrease in the number of normal, protective bacteria due to antibiotics (taken for urinary tract infection, respiratory infection, or other types of infection) allows the yeast to multiply, invade tissues and cause infection (vaginitis), resulting in irritation and other symptoms.
Suppressed immune system: Women with a suppressed immune system due to medications such as prednisone, chemotherapy, or some disease such as HIV/AIDS develop vaginal yeast infections more frequently than women with normal immunity.
Other conditions: Some other conditions which increase the risk of vaginal yeast infections include diabetes mellitus, pregnancy and oral contraceptives.
Personal hygiene measures: Vaginal douching, use of perfumed vaginal hygiene sprays, scented sanitary pads, tampons and coloured or printed toilet paper increase a woman's risk of developing a vaginal yeast infection.
Vaginal yeast infection is not a sexually transmitted disease although some men may get an itchy rash on the penis after having unprotected sex with an infected woman. The infection is more common in premenopausal women (that is women who still have monthly periods) and is infrequent in postmenopausal women and young girls (before they start menstruating). Recurrent vaginal yeast infections may be caused due to any underlying medical condition such as diabetes or HIV/AIDS, or medications such as steroids or oral contraceptive pills. Effective treatment can cure vaginal yeast infection.