i started taking biaxin xl 500 mg for 3 days on the 3rd day i knotice a white spot in my mouth the next day i woke up and knotice i had white spots all on the inside of cheeks and on my tounge it seemed everytime i looked i saw a new cluster form went to the doctor and he said it was a yeast infection in my mouth only other side effect was that i had a realy nasty taste in my mouth i stoped taking the biaxin for it scared me to death when i looked up yeast infection in mouth on the internet