Hello and Welcome to Ask A Doctor service. I have reviewed your query and here is my advice. Does your toddler attend daycare where he might have gotten a germ from another child? If he is an otherwise healthy child and has not been exposed to farm animals or contaminated water, then he probably has gastroenteritis due to a virus. In a young child who has vomiting and diarrhea, the most important thing to do initially is make sure he does not become dehydrated. I suggest that he not be given anything by mouth for the next 6-8 hours. If he hasn t vomited, offer 2-3 ounces of room temperature Pedialyte , apple juice, or pear juice. After another 2-3 hours, if there is again no vomiting, offer the same amount of fluids. Allow him to sleep. When he awakens, if he wants to eat, let him select whatever he wishes to eat. Usually the diarrhea runs its course in a couple of days. Monitor for dehydration. Signs include: -no tears -dry tongue and lips -gently pinch skin of belly, if it takes 2-3 seconds to fall back into place, - then it is doughy- a sign of dehydration -reduced urine output Should your son not stop vomiting within the next 24 hours or should he show sign of dehydration, then you need to take him to primary care doctor or to emergency room. Hope I have answered your query. Let me know if I can assist you further. Arnold Zedd, MD, FAAP