Pet external anthelmintics are mainly inhaled through the sebaceous glands and stored in the sebaceous glands. When an ectoparasite bites a pet's skin, the anthelmintic drug will enter the parasite's body, paralyzing the parasite's nerves and muscles and killing the parasite, thus expelling the parasite. However, it should be noted that these drugs are only effective against adult parasites and are not effective against eggs. Therefore, it is recommended that owners perform external deworming every month.