Our Internal Powder helps to support and strengthen the body's resistance to parasites like fleas and other biting insects. We avoid the use of yeast in the Internal Powder because of issues so many dogs and cats have with that ingredient, and instead rely on organic herbs that are high in thiamine (B1), pyridoxine (B6) and sulfur compounds. Both constituents have been shown to strengthen the skin and induce a taste that biting insects dislike. This will help prevent the itching and inflammation associated with flea and other insect bites in a natural and safe way.