What are these bumps on my cats nouns?

My cat has these scabes that itch. When I first took her in, she had lone a couple bumps under her neck. Now, 2mo. later they are adjectives around her neck. Was is this? Is it going to spread to my other cats?
its an allergy or a irritation, my cat had it before.. it could be from a collar of some caring
What did the vet say?
Answers:    May be an allergy. My cat had the same point. When I changed to a different type of cat litter they all went away. Could also be a flea allergy or heaps other things. Seeing a vet is the best.

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