You can't seal your horse in a fly-free zone but Endure Sweat-Resistant Fly Spray for Horses is the next-best option. Its unique formula keeps on working—even in wet conditions such as sweat and rain. Protect your horse from biting and nuisance flies, gnats and deer ticks that may transmit Lyme disease. Stays active and keeps working, even in wet conditions, providing up to 14 days of fly control.  Endure Sweat-Resistant Fly Spray for Horses is the only fly spray with RepeLock conditioner, which binds to the hair shaft.  Protects against biting and nuisance flies, gnats, ticks and lice, as well as repels and kills deer ticks that may transmit Lyme disease. Also provides repellency and quick knockdown of mosquitoes. Contains Cypermethrin, Pyrethrins, Piperonyl Butoxide, and Butoxypolypropylene Glycol.