Bad breath can be caused by external and internal factors. External factors can be the types of foods that we eat such as spicy or odorous in nature (certain spices used in cooking, garlic, onions even tuna or tacos). If you think your bad breath is related to the foods that you are consuming, consider recording the food you are eating to determine if this is the reason. People who use tobacco and alcohol can also experience bad breath.
Internal factors include oral factors that can affect the body systemically. The tongue provides a place for bacteria to attach and grow. Most odor-causing bacteria produce compounds that cause bad breath called volatile sulfur compounds (VSCs). These primary VSCs that cause bad breath are hydrogen sulfide and methyl mercaptan. Most of these odor-causing bacteria reside in the posterior area of the tongue.