I have taken antibiotics on a couple of occasions, once for a few months to see if my acne would clear up. I didn't feel too much of an effect, but I did have looser stools. It was actually sort-of a positive side effect for me. I didn't take probiotics very rigorously, either. I know that one antibiotic I took was Doxycycline and the other was for a sinus infection, so your antibiotic may or may not produce the same results if it's different.In the end, I don't feel it hurt or help my IBS, just gave me a short time period where I had looser stools.