Harness the natural defenses that plants use against harmful insects and put it to work for your pets. With a combination of peppermint oil, cinnamon oil, lemon grass oil and thyme oil, Sentry Natural Defense Squeeze-On will kill and repel fleas, ticks and mosquitoes naturally, not chemically. It blocks octopamine, a neurotransmitter that's found only in insects, not people, so it's completely safe around children and adults. Apply monthly, but if they're in a highly infested environment, you may need to repeat applications as necessary.