What are these black bumpy (acne like but not acne) spots on my cat? Please help

After I brought my cat back from a groomer I noticed a black bumpy (acne like but not acne) spot on the back side of the neck of my cat. After two days I saw many other such black bumpy spots on his head, back, tail and leg. When I pulled them, the hair came off with some black and white cluster at the roots of hair. I cannot figure out what those are. Can anybody help me.

Hello - I can't see this closely enough to be sure, but it sounds to be a good idea to rule out "flea pooh".  Dampen some white tissue paper and rub the black bits against it.  Flea poo will frequently leave a reddish streak behind on the tissue.  If it is flea poo, do not worry! - I'd rather my pet had that than any of the alternatives, in terms of relative cost of treatment and success of treating with a good-quality veterinary flea treatment.

Other things that your vet can rule out for you include signs of fungal disease, flaking of skin, pustules and so on.

Please do let us know how you get on