The Scientist: Emanuel Layliev, DDS, FAGD, FIADFE, Director of the New York Center for Cosmetic Dentistry

The Answer: Bad breath — in the morning and at any time of day — is usually caused by something gone awry with your oral health or your diet.

When food residue builds up between teeth, in the gums and around the tongue, bacteria comes out to play. This specific kind, called anaerobic bacteria, does not need oxygen, so your warm, moist, closed mouth is the perfect environment for it to thrive. (Yes, it’s OK to be grossed out right now.) These microscopic organisms secrete sulfur compounds, which causes that horrible rotten egg/manure smell you notice the moment you roll over and yawn first thing in the morning.

Before bed, always floss and brush teeth (and your tongue!) with an ADA approved toothpaste, which ensures it fights both tooth decay and gum disease. Use alcohol-free mouthwash, too, to further kill bacteria while preventing drying out the gums.

No one wakes up with good breath, but if yours is God-awful and you just can’t seem to get it under control by sticking to a strict bedtime oral care routine, take a closer look at your eating habits. We are sorry to say that high-protein foods, coffee, onions, garlic, sugar, dairy, and acidic foods and drinks can all fuel bad breath. Try incorporating fibrous fruits and veggies, like apples and celery, into your diet to naturally clean teeth, and eat less acidic foods to balance the pH levels in your mouth throughout the day. Drinking water regularly can also help, reducing the amount of food particles that stick around and preventing the mouth from getting too dry.

If you have chronic bad breath — something that isn’t limited to the early morning, you haven’t been kissed in months — visit your doctor: It could be a sign of a bigger problem, such as gum disease or a gastrointestinal disorder.