Pennyroyal, also known as fleabane, is a medicinal herb. It is an alternative treatment for fleas for those who do not want to use chemical insecticides on their pets or homes. Pennyroyal is toxic when ingested by cats, so take care when using the herb to repel fleas. Do not apply pennyroyal directly to the skin of a cat, or put the leaves within reach of a cat, who may try to eat it.
Place a handful of fresh pennyroyal leaves into a mortar and pestle. Grind the leaves to release the oils and aroma. Continue grinding the leaves until they are thoroughly broken up.
Transfer the leaves to a piece of cheesecloth and tie it off so the leaves won't fall out.
Rub the cheesecloth over your skin, paying attention to the ankles and feet, where fleas can easily jump onto you from the ground. Hang the cheesecloth in any room infested with fleas, out of the reach of children or pets.
Place three drops of pennyroyal essential oil on the outside of a nylon collar, so it does not come into direct contact with the pet's skin.
Put the collar on your pet.
Monitor the pet's neck for any allergic reactions. If the pet begins itching or showing signs of discomfort, remove the collar and get a new one. Decrease the dose to two drops of the oil and put the collar back on.