You might be interested in this thread in the library,
http://www.yorkietalk.com/forums/die...ural-oils.html . Tea tree oil is a “natural” ingredient used sometimes pure by owners for fleas and sometimes in shampoos, but it has been found to be extremely toxic to dogs. Don’t let the word “natural” fool you, it doesn’t mean its safe. Many people have also recommended Diatomaceous Earth (its natural) sprinkled all over the house and even on the dog. However, new findings show that you should never put it on your dog, and you should vacuum it all up before for your dog comes into contact with those areas. It may kill the pests, but it can cause lung cancer. The problem with natural ingredients is that because they aren’t specifically made for any one thing, they may or may not be effective at what you want to use it for and they may or may not be safe. Companies who make products for special purposes have to test that they are effective and safe. So if you really want to be safe, use something that has been tested. People confuse the word "chemical" with the word "toxin" and this is a huge mistake.