Earlier this week I had just asked myself why were onions bad for dogs? I meant to look it up online but never got around to it [as I donâ€™t have a dog it is not a pressing matter]. Then tonight while in waiting room at the doctorâ€™s office I was reading a National Geographic from October 2007 when I came across an article on the pet food contaminated with melamine and how normal people food is bad for dogs. It goes on to list other things to watch out for and well thanks to that article I now know that onions damage a dogâ€™s hemoglobin. And that it is cumulative, so even a little onion every once in awhile can be as bad as an entire onion bulb over time. So keep your doggy away from onions.