Description Defy the Fly Dog Fly Collar is a all natural patented fly collar that contain no harmful chemicals and offer protection for up to 2 months. Worn as shown, the collar will give relief from flies that normally swarm around your dogâs head. Also repels fleas, mosquitoes and ticks. Keep dry, do not get wet. Now labeled to be used on goats, sheep and small ponies as well as dogs.