My son is almost 18 months and has had two viruses. One was herpingina which caused sores in mouth and excessive vomiting, the other was just a stomach bug that caused vomiting. These virus started one moth from each other. It has been about two months since the last virus and my son had went to bed throwing up. Nothing else again till the morning. There was lots of gagging but nothing until about 9 that morning. He threw up right after the milk bottles that he had. It was not much but still enough to be considered throw up and not spit up. He also eats the same things daily and has the same amount of milk daily. I feel like it is not excessive eating or lactose just cause we basically do the same thing everyday. He is fine, no fever no diarrhea.