Sounds like fleas
& if so your other cats likely already have them
Flea collars don't always work I personally don't like them, not only the smell but the pesticide content in close constant contact w/the cat
Flea baths - same thing loads of pesticides fleas can also survive in water for short periods of time.
Not only do you need to get rid of the fleas on the cat but also in the house. Fleas lay their eggs in the carpets, furniture, bedding in the house. Everything needs to be washed/vaccumed frequently when there is a flea issue. Eggs also can stay dormant for along time so even if you don't see fleas for a while there still may be some around.
You can call the vets office & bring the cat in to check that is it actually fleas, & then get Revolution, or Advantage to kill the current adult fleas while you do a through house cleaning. Usually the reception staff or a vet tech can help you with the flea identifying without having to book a full appt. Call to make sure they will do that for you.
Don't use the over the counter products, the safety level of some of those products is questionable at best, down right toxic in others.