Generally, cats are covered with fleas and few lice. I guess you mean fleas.
Treatment: Freine spray or drops are particularly effective and have less side effects. If you don't help the cat, it's a waste to buy spray. You can buy a spray or go to the pet hospital to use it once. Drops are said to be better than spray, but it's hard to say if you buy fake ones. After taking the medicine, I can't remember whether to take a bath for 24 hours or 48 hours. You can keep the cat in a closed carton for 24 hours.