Vomiting can erode your tooth enamel due to the acidity of your stomach acid, but nausea by itself is also detrimental. If you are feeling nauseous, the simple act of putting a toothbrush in your mouth to brush can make you feel like you’re going to be sick, which might make you forgo regular brushing. While understandable, skipping regular brushings can allow bacteria and plaque to accumulate, leading to increased risk of tooth decay.