think about it oldyellow people are given antibiotics sometimes even to save their lives with no side affects although i have only used them once in 30 years i only did cause i had to as mine only had ybs once 2 yrs ago some wer at deaths door but with baytril they pulled through but maybe using it to often or to strong might have side effects i dont know i know some good racers even use it as a preventitive although i woulnt go that far iam only reccomending it as a cure for yb sickness it worked for me allmost overnight it would b interesting to here other fanciers views who have used it on this if i can help someone i will.