1.5 Year old reaction to IVIG?

My 1.5 year old was diagnosed with ITP and we had a hospital stay and an IVIG treatment. Its been about 48 hours since his treatment. He has been very active today and just ate a ton of food pretty quickly and then he threw up. He is otherwise acting normal. I am, of course, a little bit worried that this is a reaction to the IVIG, but it could very well just be him eating to quickly after playing too much. He is sleeping now (about 45 minutes before his normal bedtime.) Its so hard to tell whats going on since he is so young and cant tell me he has a headache or if he is nauseous. Should I be worried? Does anybody have any experience with IVIG in a child this young?

He was so happy to be home from the hospital and throughout this whole ordeal has acted normal, its hard to remember that he just had a huge shock to his little system.

I don't know much about IVIg as my son only had it the once. However, I think that if your little man is otherwise behaving normally, then he is probably ok - my memory of 1 year olds is that they do just chuck up for no apparent reason sometimes!!!! IVIg can be horrible stuff though. When my son got the headache, he just stopped, didn't want to move, thought everything was too loud, felt sick, etc. If you get to the stage where you really feel nervous about his reaction though, call the doctor - I think they would expect you to do so. Good luck.