For centuries humans have used rosemary in small quantities to aid in digestion, soothe stomachaches, cure headaches and to refresh and strengthen the skin.
Rosemary not only benefits humans --- when used correctly, it can effectively repel fleas from pets. It has also been proved to kill fleas on contact.
There are several ways to use rosemary as a flea repellent, including making a flea powder to rub into your pet's coat or brewing a rosemary tea to pour over your pet after a bath. You can also apply a few drops of rosemary essential oil to your pet's collar or sleep area to discourage fleas.
Although in most cases consuming rosemary is safe, there are exceptions. According to a study in the Journal of Neurology, in some rare cases rosemary has caused epileptic seizures in humans and animals when taken internally. While it seems to happen only in people or animals that are already prone to seizures, you should use caution. Never use rosemary in ways pets or small children might be able to ingest it. For example, be careful when using it on your pet's coat, since the animal could lick it off when grooming.