Kitten throwing up

I have been noticing one of Angels's kittens has been throwing up. They are 10 weeks old now. What could be causing this? Also, somebody sent me a link before on kitten maintenance like when shots are due and that kind of stuff. Could this be cause him to throw up cause he hasn't been to vet yet?

Cathy

Cathy if he is throwing up and hasn't been to the vet, the whole family needs to go, but if you can't swing that at least take the kitten (and the mom) in. The sooner the better.

nobody else is throwing up but just the one kitten. He doesn't act sick, still running around and playing. I have noticed that he has been nibbleing on the other cat food (one is 9 lives and one is SD kitten food for my diabetic cat). Could maybe that be it also? The change of food? I'm fixing to clean up my carrier and put him in there for today. Vet's aren't open today so it will have to wait until tomorrow on the vet.

Cathy