There are two types of external deworming for cats: drops and sprays. To use drops, you need to remove the hair on the back of the cat’s neck first, and then apply the drops on the cat’s skin. Wait for the medicine to fully penetrate into the skin before loosening it. Open the hair; the spray needs to wet the hair all over the cat's body, and wear an Elizabethan collar on the cat during this period until the hair dries naturally.
Tip:
Cat anthelmintics are somewhat toxic, so be sure not to let cats lick them, and take one pill per cat.