Substances that repel fleas include lavender, lemon balm, catnip, citronella and peppermint. Growing these plants near windows and doors or keeping them as houseplants repels fleas, mosquitoes and other biting insects. Essential oils from these plants are also effective insect repellents.
To repel fleas with peppermint, lavender or lemon balm essential oils, mix several drops of oil in a clean spray bottle filled with tepid distilled water. Spray the mixture on clothing, bed linens, pet beds, carpets, drapes and other textiles. Add more oil for a stronger fragrance.
Cedar oil is a powerful flea repellent that is particularly effective when infused into homemade dog collars. Mix a few tablespoons of warm filtered water with three or four drops of cedar oil then use an eyedropper to dribble the solution over a clean dog collar or a bandanna. Place the bandanna or collar on the dog's neck, and refresh the oil once a week. For extra protection, mix together one tablespoon of olive oil and a few drops of lavender or cedar oil. Apply two or three drops at the base of the dog's tail once a day.
Marigolds are also effective flea repellents. These bright blossoms also add pops of color to gardens and window boxes.