The most direct signs that a cat needs external parasite treatment are patches, rashes, and dandruff on its skin. These are the most obvious signs of skin problems, and the direct cause of skin diseases is external parasites. Therefore, once these symptoms appear, the owner needs to treat the cat for parasites promptly. It's best to treat your cat for external parasites once a month, especially for cats that like to spend time outdoors, as this effectively prevents the development of external parasites. 
What to pay attention to when deworming cats:
1. Dosage of deworming medication for cats. Deworming medication is toxic, so it is essential to administer it according to the instructions, especially for domestically produced deworming medications. Always weigh your cat before administering the medication and calculate the dosage based on their weight. Sometimes there may be leftover medication; if you feel it's wasteful, you can give it to stray cats.
2. Deworming your cat should be done regularly, about once a month. Cats are the definitive host for many parasites. Depending on the type of parasite, some have a life cycle of half a month, while others only last a week. Therefore, deworming once a month is absolutely necessary.
3. Do not use flea collars for external parasite control. Most flea collars are made with dichlorvos, which is highly toxic and very harmful to cats.
