Tea Tree Oil is safe for dogs when you dilute the Tea Tree Oil.
When using Tea Tree Oil on your dog dilute it first before applying the Tea Tree Oil to your dog.
If you don't dilute the Tea Tree Oil first it can irritate or burn your dogs skin but diluting it will be okay to use the Tea Tree Oil on your dog.
I use Tea Tree Oil both on my dog and my two cats after I dilute it.
Diluting the Tea Tree Oil for use on your dog with some water is a ratio of 0.1-1.0 percent strength, to be dispensed topically.