I have a few questions:
How long has he been vomitting.
What does his diet consist of.
Is there blood or mucous present in the vomit?
Is he a very excited dog?
Does he lick his fur alot and vomit "hair balls"?
Does he have dry skin?Please answer these questions, the best you can and I will get back to with a response.Parisites are a common cause for vomiting in dogs. It is impossible to determine what it is without seeing your vet. It is important that you find out what it is in case it is something serious. I encourage you to see your vet asap. I hope I helped a little. Have a good night.