Bumps on neck of cat

My friend has 2 cats but one has bumps on the back of his neck he dosent wear a collor . She is worry she does not know what to do please help thanks laura

Are the bumps under the skin or more like a rash? Also, how big are the bumps?

Does the Cat have fleas ? It may have a flea alergy? Does the cat go outside & Fight? Also is the cat a male?
I think to help we need a bit more information , Good Luck!

One of my cats developed the same symptoms (little scabs & bumps around her neck) at a late age. I took her to the vet and the first thing he asked was 'does she eat canned cat food with fish?' Turns out she had developed an allergy to fish which is not uncommon in cats.

Michael