Some kind of paw infection or allergy? Help!

Hi everyone!

I saw my cat chewing something on her right foot this morning, so I checked it out. She has some nasty looking scabs/calluses on most of her front right pad, and parts of her rear right pad, but nothing on the left feet at all. I've never checked her feet regularly, so I have no idea how long it's been there. I have no idea what to do or what is causing this. I've had the cat for over 4 years, and it couldn't have been going on that long so it's something fairly recent. I switch cat litters all the time (whatever's on sale) and she's never had a reaction to any, but I'm wondering if a particular brand I bought recently maybe did it? Has anyone seen something like this before? I believe she digs in the litter box with her right front foot, so that makes sense, but I don't know why it's on her right rear foot. Is it common for a cat to use two feet in a litter box, but not the other? Is it not the cat litter at all? Thanks so much for looking and any help would be HUGELY appreciated. The picture of her front right foot is below.

I have no personal experience but there is a condition called pillow foot.  http://oldmaidcatlady.blogspot.com/2014/08/spotlight-plasma-cell-pododermatitis.html    http://www.pethealthnetwork.com/cat...sma-cell-pododermatitis-my-cat-has-a-sore-paw It is autoimmune in nature which means there could be a cause that can be identified or there may not be.  Some kitties recover spontaneously and others need treatment with steroids.  I think a visit to a vet would be best.

Did you ever figure out what happened? My cat has the same thing!

OP has not been back since the original post, so you will probably not receive a response.