Several studies have been done on the effectiveness of citronella collars as dog training devices, and have found that the citronella spray collars are more effective in training a dog not to bark or commit other unwanted behaviors.
They are also widely recognized as being a lot more humane to your dog than methods that cause physical pain to him, such as electronic shock collars, and ultrasonic devices that play a sound that hurts your dogs ears.
Citronella Collars work by spraying a squirt of citronella oil under your dogs chin that distracts him from whichever unwanted behavior he is committing, and he learns to associate the behavior with a spray of Citronella oil, and will avoid the behavior.
The collars come in two forms, sound activated versions and remote control versions.
The sound activated collars use a small sound sensor that is embedded in the collar to trigger the spray.
These are useful for training dogs not to bark.
The sound sensor will detect your dogs bark, and release the spray of citronella oil under his chin.
The remote control versions are great for other behaviors such as using the bathroom inside, chewing on your footwear, digging in the yard, jumping up on furniture or people, and many other behaviors that do not produce a sound like barking does.
The remote collars have a small pocket sized remote control that lets you press a button every time you see your dog commit the behavior, and he gets a squirt of citronella oil to distract him from the behavior.