My Lab and her illness

Question
I have a creme color lab that is about 1 and 1/2 years old. She has always done ok with the kids. Lately she growls at them and doesn't want to be bothered by them. They don't tease her or anything. She has been throwing up off and on for several weeks. I have taken her to the vet twice and they can't find anything wrong with her. She has always had a very protective nature. She barks and growls at most people outside the house. The vet said she might have nerve problems. I have never heard of any of the symptoms in a lab. They are very loving and kind and good with kids. What is going on with her disposition and her health? Thanks for any help you can give.

Answer
You could try another vet for a second opinion.  

Another possibility is looking at what else is going on in your life.  If this is a bad time for you, you could be passing on your stress to the dog.  

She might keep her food down better if she ate slower.  Try spreading it out on a cookie sheet or something.