Hairballs and Bare patches of skin

[krispifsu]

I need some advice for my cat Oreo. He is almost three years old and is neutered. He is fed Science Diet Hairball control everyday because he has medium length hair. The problem I am having with him is that he has been vomiting huge amounts of hair quite regaurly for a few months now. He has been to the vet twice for this and each time they say they cannot find any reason for it and gave me laxatone to take home and give to him. He has been given the laxatone pretty much every day but still continues to vomit. He'll maybe vomit a few times a day for a day or so and then stop for a few days and then start again. he probably vomits about 5 times a week with either huge amounts of hair or undigesed food or both. I'm away at school so my mom and dad are taking care of him until i move into a house in August. They've been giving him the laxatone pretty regaurly and also try to brush him a few times a week (but he doesn't really like it much). I came home this week and found a large (tennis ball sized) patch of hair missing from his stomach. It's all the way bare but have a very noticeable hair loss in that area. He seems to be acting fine and still eats and drinks normally. he is going back to the vet unfortunaltey they could not get him in until two days from now. What I need help with is figuring out possible causes that I can bring to my vet's attention that others have had experience with. i'm really worried about him and have no idea what could be causing this. Any help would be extremely appreciated.