There are many reasons for bad breath in the morning, such as the following reasons: First, bad breath in the morning may be due to eating foods that cause bad breath, such as garlic, seafood, stinky tofu and other foods that can cause bad breath in the morning; Second, bad breath in the morning may also be due to drinking less water; Third, bad breath in the morning may also be due to less brushing, there is no regular healthy morning and evening brushing; Fourth, bad breath in the morning Bad breath may also be due to oral diseases, or diseases of the digestive system can also cause bad breath, such as acute and chronic superficial gastritis, erosive gastritis, atrophic gastritis, enteritis, etc.. In short, there are many reasons that can cause bad breath in the morning, and need to be analyzed on a case-by-case basis.