No, a pet collar that repels fleas is not considered a pesticide. Pesticides are substances or mixtures that are applied to target pests, such as insects, weeds, and microorganisms. A pet collar that repels fleas effectively deters certain pests, but not by killing them; instead, it prevents them from living on the pet. The active ingredient in these collars usually comes in the form of natural oils with insect repellent properties such as citronella oil and peppermint oil. Additionally, some pet collars may contain insecticides like permethrin or methoprene to further kill and prevent fleas from making contact with your pet, however these types of collars are less common than those which rely solely on natural pest-repelling ingredients.
Final note
A pet collar that repels fleas can be considered a pesticide since it contains insecticides with active ingredients designed to target and deter potential pests. It is important to understand their effects and research safe alternatives before using one of these collars on your pet.