3 yr old vomitting, and diarrhea. says stomach upset and can't hold anything down for almost 24hrs. when should i go to emerg?

Now: Chances are hes become dehydrated.Take to the er before things get worse.

Dehydration: If vomiting and diarrhea do not stop after 24 hours child may become dehydrated. Major signs of dehydration are sunken eyes, decreased frequency of urination or dry diapers , no tears, lethargy and dry mucous membranes.If these signs are present, should seek advice of pediatrician or emergency room physician for therapy to correct dehydration..