A person can get a yeast infection from antibiotics, steroids, diabetes, pregnancy, a weak immune system, hormonal changes and allergic reactions, according to eMedicineHealth.com. Major diseases, such as leukemia or HIV, can also cause yeast infections.
WebMD mentions that a yeast infection occurs when too many yeast cells dwell in the vagina. The type of yeast that causes the infection is known as Candida albicans. An infection happens when yeast cells offset the number of bacteria in the vagina. Normal bacteria can normally keep Candida albicans under control, according to eMedicineHealth.com, but antibiotics can eliminate crucial bacteria that protect the vagina. Diabetes can cause a yeast infection as well by upsetting the normal levels of bacteria. It also increases sugar levels in the blood, which can lead to a vaginal infection.
A yeast infection can also occur from an allergic reaction to chemicals, such as soap, powder or perfumes, according to eMedicineHealth.com. Douches and feminine hygiene sprays are other irritants that can cause a vaginal reaction. Tampons may spark an allergic reaction if they scratch or damage an area of the vagina. Tight underwear is another cause, especially with non-cotton materials. Excess moisture and an increase in temperature may also be the root of the problem.
HIV or AIDS can cause the immune system to weaken, according to eMedicineHealth.com, which can lead to a yeast infection. Pregnancy, cancer, drugs and chemotherapy are other things that may compromise the immune system.