No. Ruby Cup does not absorb or interfere with the natural pH of your vagina. Thrush is caused by Candida, a yeast fungus and can occur when the natural balance of your vagina is disturbed. Tampons absorb protective secretions that prevent thrush, menstrual cups do not. Avoid using perfumed soaps to clean your cup and when washing your delicate vaginal area as this can also disturb your pH balance.