Dog insect repellents can come in various forms, including sprays, spot-on treatments, collars, and even natural remedies. The purpose of these repellents is to protect dogs from the annoyance and potential health risks associated with insect bites, such as itching, allergic reactions, and transmission of diseases like heartworm or Lyme disease. When using dog insect repellents, it's crucial to choose products specifically formulated for dogs, as some ingredients commonly found in human insect repellents can be toxic to dogs.