Hair loss and scratching...winter dry skin, food, bugs???

My kitty Curtis (who is a girl btw lol) has within the last several weeks grown a bunch of bald patches on her front and hind legs from obsessively licking and grooming.  The skin on these spots is not red or inflamed, in fact it's not really completely hairless, but it looks like she got sheared with clippers and the skin underneath that is kind of flaky and dry.  She's also started scratching around her head and neck a lot and her overall appearance just looks rough and crummy.  She's otherwise acting fine, she plays normally, drinks and eats...though to say she eats normally ever is kind of misleading. She also has a tendency to randomly puke and the only food she would tolerate for a long while (including some grain-free) was Purina One, which though not the best, was better than not keeping any nutrients in at all obviously.  Well, at about the same time as the vigorous scratching and grooming started, the vomiting started again and we're currently moving to wet food with another grain-free dry as supplement to see if that makes any difference.  

All of my house cats are treated in the summer months with Revolution and kept indoors during the winter months so I'm almost certain it's not fleas, though I did comb through all of them pretty thoroughly just to be sure, and I have not seen any evidence of bugs at all.  My other two are scratching a fair bit as well, though definitely not on the same level as Curtis is---she'll be happily playing one minute and then all of a sudden it's like stop the press she'll plunk down and scratch the dickens out of her neck for 20 seconds or start licking and chewing her leg off.  I've hesitated thus far to bring her in, as I know she has a history of allergies (chronic sneezing when we used to use indoor wood heat) and I don't really wanna shell out $100 for them to tell me surprise "oh she has dry skin" or "try switching foods" but I can't take it anymore, I feel so bad for her and will be calling the vet.  In the meantime though, does this sound familiar to anyone?  Do food allergies manifest like this?  Maybe a humidifier or a mister would help some..? ugh I have no idea.

Food allergies DO manifest like that, particularly the scratching around the head and neck.  Has your Vet ever given Curtis anything for her itching?  Sometimes they are given a steroid to help, sometimes even just a course of antihistimines (like Benedryl) until the food culprit can be determined and switched.

Maybe this thread will be helpful to you:  http://www.thecatsite.com/t/312786/cat-allergies

thank you! The vet had never given her anything for her allergies before, but did mention they can take benadryl or zyrtec (if I remember correctly) and I do have zyrtec on hand, but that was in regards to her chronic sneezing, not the food issues.  We're just going to continue with the food change and see if that helps. No vomiting yet so my fingers are crossed

Entirely possible it's a food issue. I would look at feeding her better quality food ASAP and something that isn't grocery store brand. Remember, cats are obligate carnivores so they need meat, not veggies or corn, or wheat or other strange things that show up in cheap grocery store food. Wet food is also really important when you're dealing with dry flakey skin, which can also be from dehydration. Some decent/good ones that are fairly low cost are - 

Fancy Feast Classic chicken

Sheba

Nutro natural choice

Wellness

Nature's Variety

Merrick

Soulistic by Petco 

You might hop over to the nutrition threads for more suggestions.