What is the most effective spot on dog flea treatment available on the market?

The most effective spot-on dog flea treatment available on the market is typically considered to be products containing ingredients like fipronil, imidacloprid, or selamectin. These treatments are applied directly to the skin on the back of the dog's neck and are known to effectively kill and repel fleas for a month or longer. It is important to consult with a veterinarian to determine the best option for your specific dog's needs.