Know the benefits of using peppermint as flea repellant and ways to use it on your pet. 2. Though peppermint does not fully work to kill the fleas but it helps in restricting the attack on pets. Use it in a correct way and you will have a healthy and flea free pet at home. 3. Keep the peppermint oil in the spray bottle to repel fleas. Mix 3 small cups of rubbing alcohol with a quarter cup of peppermint oil and allow the solution to get settled. Pour all the solution in a spray bottle and spray it on affected areas specially neck, back etc.