Unfortunately, despite what manufacturers may claim, collars alone are not very effective at controlling fleas. Ask your vet for recommendations bout the best collar for your pet. Your vet should be able to recommend, and even provide, the best flea collar option for your pet. These collars are best used in vacuum cleaner bags, where the gas is contained, and can be effective against fleas that are vacuumed up. These can contain pyrethrins, as well as IGR's, or insect growth regulators that inhibit flea egg and larva growth. Flea collars that release toxins that are absorbed into the fat layer are much more effective.

For many people, treated flea collars seem like a safe and convenient method to control fleas on their pets. The toxic gas method is usually only effective in the immediate area of the collar, i.e. Flea collars generally work in one of two ways either by emitting a toxic gas, or by releasing toxins that are absorbed into the layer of fat beneath the pet's skin. Remember, controlling the peirce stages of the flea life cycle is just as important as killing adult fleas.

Some ingredients, such as permethrins, should not be used on cats.