Even though garlic is really good for your health and can add delicious flavour to your food, they are known to cause terrible bad breath. ‘When you eat garlic you produce several sulphur-containing gases. But what we found is most of the sulphur-containing gases, with exception of one, [are of oral origin]. AMS [allyl methyl sulphide] is the only one that is not metabolized by [intestine] or the liver, and this is why this gas can go back and be released in your mouth. It\'s coming from the [gut], not from the mouth, and that is what gives you the odor that you have after you eat garlic.’ Fabrizis Suarez told WebMD.