A flea collar is a type of pet product that is designed to prevent or control infestations of fleas on cats and dogs. The collar contains an insecticide, usually in the form of a slow-release substance, which kills fleas as they come into contact with it. Flea collars are typically worn around the neck of a pet, where they can be easily accessed by fleas that may jump onto them from nearby surfaces or other animals. The collar works to control and prevent infestations over time, reducing the need for frequent applications of topical treatments.