Jennifer, We've been through this for 15+years with our son and I can tell you that you will know when yours is in need of an ER visit. When Ben was young, he would get lethargic and kind of pasty looking and would get very sick quickly. We only have had a handful of trips to the ER thankfully but each one was necessary. If you child vomits once, don't panic; twice, get ready and if a third time without keeping his meds down, go to the ER. We were out of town last month and Ben was home with his 29 year old brother when he developed a fever and vomited once. His brother knew to call me but Ben still sounded fine. By the third vomit, he was out of it but still told his brother he needed to go to the ER and needed IV fluids and 100 mg of Solu-Cortef. This was the first emergency visit in 9 years, but he still remembered what it felt like. We were pleased that they handled it so well since college is not that far off. Good luck and ALWAYS listen to your gut feelings! Mary