cat losing clumps of hair

My 13 year old longhair cat has been loosing clumps of hair over the past 2-3 days. It is strange because of the number of them and because they are in clumps. I checked for fleas and that doesn't seem to be the problem. He is an indoor cat, but got out (overnight) about 3 days ago.

[Aleda M Cheng, D.V.M., C.V.A]

Please bring your cat to the veterinarian and have a complete blood profile performed with a thyroid panel.  Also,  have your veterinarian check for mites and other skin parasites.  There are several types of cat mites that cause extreme itching and are quickly contagious from wildlife.  Your cat may have been exposed to these parasites when outside for the one day.  Ear mites can cause extreme itching around the head, so your cat should also be check for those as well as ear polyps.  Injectable depo-medrol or oral prednisolone would help your cat if your cat has had an allergic reaction to an ectoparasite.