Sick Shitzu

I have a shitzu that is about 5 years old, male, he has a very sensitive stomach.  Today he has been throwing up constantly, like white stuff, not food or vile and has been very weak.  Usually if he eats something he shouldn't he does throw up but its that food.  Today he hasn't eaten anything that i know of.  

[ginger899]

Part of his weakness could be caused by dehydration. Yet when a dog is in a constantly-vomiting cycle, if he drinks, it may cause him to vomit more....etc.
So really the best thing you can do is get him to a vet. A dog that vomits more than once or twice, bringing up no food, and doesn't improve after vomiting, needs some medical attention. He may need to be rehydrated by I.V. and the cause of his sickness found out, and treated quickly.