They honestly aren't. It could cause death to small dogs. But it works on big dog breeds. There are safer ways to get rid of fleas though. I use a recipe I found on the internet, it's vegetable vinegar and Dawn dish soap mixed together. It's around 1/2 to a cup each mixed together. Once you have them mixed together you use it instead of dog shampoo— it kills fleas, flea eggs, ticks, and takes off A LOT of dirt. It works really well for my dogs and cat. It leaves them look really clean.