Cat losing fur, family having red itchy spots

Question
My large cat is losing fur, (weighs 13 pounds), and lately my family and I have been getting red itcy spots on our legs and abdomen. I'm wondering if these are connected, I took the cat to the vet, but he wasn't sure what was wrong, and suggested that I change the cats diet. I have been feeding him the Science Diet, Charlie (my cat) is an indoor/outdoor cat, that is, my mother doesn't allow a litter box so he does his business outside, but usually spends most of his day indoors.
I have five cats, but only one other is losing fur, and her's is just a small spot on her back, my cat Charlie has fur missing all over. I was wondering if they have some kind of lice or something that is making their fur disappear, and is biting us. Any help you can give would be appreciated, Thank you.

Answer
He isn't sure what's wrong? Did he do a skin scraping on this cat? Did he check the cat for fleas, ringworm, or scabies?

Ringworm ( a fungus) and scabies ( a mange) are both transmissible to humans and fleas will bite you like crazy when there are enough of them around.

Round, red, itchy circles are the sign of ringworm on us and bald, flaky, scaly and sometimes red patches are the sign of it on the cats.

You need to get this cat back in to the vet's or you need a new vet. I can't tell you how many people came in to use covered with ringworm because the doctor they saw never mentioned it and the cat was full of it.

Once the  cats are being treated you need to be treated. If it is a flea problem, then you need a full force of IGR flea products, such as Ovitrol spray and other insect growth regulators.

Your cats need to be treated with creams and pills such as Grisiofulvicin and some Providine scrub.

What ever you do, don't change the food. Science Diet is the best food out there and this is NOT a food problem. You might want to find an older vet that has some experience with skin disorders such as ringworm.

If the one cat has a bilateral type of hair loss, that is on both side equally, then you might be dealing with a hormone problem, which in either case still needs a vet exam and some bloodwork. But we always look to the simple side first, and that would be ringworm or scabies.

Once you find out what it is, please let me know.