Hair Loss?

I have two black Maine Coone (North American Longhair) cats. They are 2 1/2years old, and are twin brothers. They are almost identical, but one is losing hair in small patches. His abdomen and portions of his back are losing noticeable amounts of hair. The weird part is that the skin in the hair loss area looks fine..there aren't any signs of irritation. Is this normal in adult long hairs? I have a vet appt. in a couple of weeks. Any help would be appreciated. thanks

p.s. I just found this..Maine Coon's have abundant fur and sensitive skin..The fur should be dense, fine and soft to the touch. The sparse undercoat is soft and fine, covered by a smooth fur that’s impermeable and hangs down to the ground.

"Breeders cite greasy hair, scurf and hair-loss as some of the breed’s most frequent skin
complaints".

It could be allergies?

what is the cat eating ???
last vet check??
when you see the vet ask them to culture the spot ...

with cats fish , corn and wheat are high allergens...

Thanks for the tips..it must be allergies, because I just started letting him nibble small leftovers off of my plate (tiny, small bits of tuna, and a little tiny bit of wheat cereal with milk)..something I told myself I'd never do..they have great manners, but I knew it would be irritating to have them jump onto my lap while eating. I also changed their dry food from Purina Cat Chow indoor formula to Purina (in the purple bag?)..I can't find it on the purina site..bought it at Winn Dixie..the name was Purina "bits" of some kind..
So, I switched em back to the Cat Chow indoor formula in the green bag from Purina..they love that, as it has greens in it..it also has some Salmon in it, though..

They go to the vet next week..

GOOD about the vet trip..

Can you buy food NOT at the grocery store?? if you read all the labels corn and chicken by products are usually the first two or three ingrediants

thanks all, for the great advice..I started feeding him treats for tartar control as well..that may have been it, as I had never given him that before..they are fish tartar control treats..I have a vet appt. soon. thanks again!