So what's in your hair?

I went to a mommy gathering today at another's house. As 10 moms look at me, I'm holding a screaming baby and trying to sooth her. V. comes and stands by my leg being shy in the beginning. Finally one of the other moms looks down at V. and asks- what's in her hair. I look down and she is coated in white slime. At first I had thought it was the dog that had gotten loose and maybe licked her. As I clean her up, I notice the smell, and put 2 and 2 together. Her sister puked on her head. What is wrong with my child? She pukes all the time. I've tried a ton of different medicines (natural, over the counter, and prescription), but nothing seems to work. I love I. but I can't wait for this phase to be over.