Each time your dog barks, the sound-sensitive Anti-Bark Spray Collar releases a spray of harmless citronella . The spray interrupts the dog's pattern of barking. Over time, most dogs are gradually conditioned to stop barking. The product includes a refill can of citronella spray, and complete instructions on how to use. This is a safe, effective and humane way to end your dog's cycle of nusiance barking.