Yes, one of the side effects from fish oils is they may cause bad breath, burps and gas. This is usually seen in lower grade fish oils where they were not properly processed or may contain rancid fatty acids. Using a pharmaceutical-grade fish oil may help reduce these symptoms. I found that even with some high grade fish oils I would get the occasional bout of 'fish breath'. I resorted to gargling with Listerine and found that effectively destroyed all traces of fish breath and left me with clean fresh breath. Good luck and I hope this information is helpful.