Cat has a sore spot under chin/neck

Took her to see her vet last weekend. Thought it may have been started by my other cat. Giving her antibiotics. Possibility of
? inflammatory blah blah granuloma. Area is getting worse, very raw looking, likely from her scratching it. Have tried many methods of covering the area but it's an awkward spot...and she's a cat! Getting concerned that it is not an injury but may be a skin condition. I need input:
1.) Any ideas what it might be / what's causing it?
2.) How do you keep a cat from scratching itself? The hooded sweater (aka old sock) did not work!

Tricky one since you can't be sure if the anti biotic is working due to the scratching of the wound. As you know, you must keep the cat from scratching the wound in order for it to heal.

I'm not sure if the sock thing is like the Elizabethan collar, but here is a picture of the apparatus you need to buy or construct. They are not that expensive to buy.

http://www.advertising.ca

U.F.