Overgrooming possibly a food allergy?

At the beginning of October we noticed our cat was beginning to groom herself excessively to the point she was forming bald spots on the backs of her legs, the tail, sides, and stomach. We thought it may be some stress with the changing of the weather and my work schedule changing from days to nights. We got her a companion to help keep her company. They get along great. This didn't stop the excessive grooming. The grooming must have turned into itching because she started forming scabs. Between her ears, above her eyes, and on her ears are the worst scab locations. We thought it could be a food allergy and changed to canned food only. It's been a week and she's still cleaning herself excessively. I'm worried it could be something more. I feel so bad that I can't fix this for her. Does anyone have any experience with similar behavior?

Have you tried any calming agents to help de-stress?  What were you feeding her and what are you feeding her now?  It's going to take a bit of time for it to get out of her system.  Could it be a flea allergy?  Have you taken her to the vet?

She was eating dry food before but has been on a canned food diet lately. The vet is our next option if it is not a food allergy. What kind of destressing agents are available?

Also, we haven't seen any fleas since June of this year. We recently took the new kitten to be spayed and they noticed a couple ear mites that she was treated for. It started at the rear of our cats body and now the head is taking the worst of it.

Feliway is one calming agent.  Rescue Remedy and Spirit Essences blends are other calming agents.

You can try a limited ingredient food, such as duck & pea or an all meat food without grains and see if that helps. 

I would encourage you to get her to the vet to get her some meds to help stop the itching until you can figure out what's going on.

I'm sorry to hear you kitty is having trouble.

My cat has a similar problem. I switched her food and she started losing her fur, she was lethargic, etc..... I switched back to the other food she was on and she did fine. But I still took her to the vet because of it (and it was taking a while for her fur to grow back) and the vet said it wasn't an allergy but due to fleas. She has not had fleas since 2008. I know this because I treat her and check her meticulously because I work in an environment where it would be easy to bring home a flea. After about 3 months or so of her being on Chicken, I decided to switch the flavor, so I got her a Salmon formula. After a few weeks of her being on that flavor, she started losing her fur, I noticed bare spots on her sides and belly, she even had a scab on her leg where she had been chewing, and had itchy bumps on her ears.  I've determined she's allergic to salmon.

An allergy usually takes about 6 weeks or more to get out of your animals system. I would think this is what your cat is experiencing. You can try a grain free diet or a Limited Ingredient Diet food as suggested above. If you take your animal to the vet, I've been told that allergy tests for an animal are very expensive. 

Also, as suggested, you can try calming remedies. I use NaturVet Quiet Moments for my cat. It has Melatonin, Chamomile, L-tryptophan, etc... it in. You can also try Sentry calming collars, Feliway diffuser/Comfort Zone by Feliway diffuser, calming sprays, etc... There's also a product that is sold a Petco. I can't remember the name of it, but it is sold in the dog aisle (it's for dogs and cats) in a blue glass bottle with a dropper on it. A friend of mine uses it and she says it works great for her dogs and cats. 

Hopefully you can find out what is going on! Good luck!