Huge wound, tiny scabs

Question
I currently have 2 female rats living in separate cages (as they do not get along very well) and one is a little older than the other. About last month I've noticed a wound or a sore or a... well, something on my oldest rats shoulder. It isn't a scab because I think she keeps scratching it off before it can heal enough to scab up, but its awfully big and wet and I'm worried. As I'm stressed out about THAT, my younger rat has tiny scabs under her chin and on her back. I read somewhere that it might be mites but I don't know how to determine that or if its their diet.

I have absolutely no money to go to a vet right now, so I was hoping there were home remedies or things I can do where I can simply buy stuff from a pet store.

I hope theres a way to help them without blowing a whole bunch of money on a vet. Thank you for your time!

Answer
 Tiny scabs under their chin are usually a sign of the rats fighting.  They often nip at each other's faces and leave little scabs.  Mites usually only bite on the hairless areas of a rat such as the ears, feet, and tail base and you will notice them itching at those areas.  Lice are big enough to see with the naked eye, just part the fur on their backs and you will see red bugs crawling around.  If you see neither of those it is probably just from them fighting.  Mites and lice are actually very easy to treat; you can buy a tube of Advantage or Revolution (the puppy / kitten kind) from your vet for under $15 and using a 1cc syringe or an eyedropper place a single drop on the back of their necks against their skin (make sure you don't get it in the one rat's wound).  This will kill any parasites they have and is safe to use even if they don't have any.  You'll have to repeat the procedure in two weeks, making sure to clean their cage and every item in the cage very well between doses.  There should be enough in the one tube for two rats and two doses so it won't cost you much at all.

 As for the wound, it sounds like it may be infected, in which case all you can do is take her to a vet to get her on antibiotics.  For now you can scrub it very gently with an antibacterial surgical scrub (you should be able to find some at a pharmacy, or your vet's), but it probably will not heal very well if she keeps picking at it.  If it is weeping green, white, or brown liquid and feels hot to the touch it is definitely infected and will need to be properly cleaned by a vet and she will have to be given antibiotics and likely painkillers.  Rats will often pick at a wound when it is hurting them, in an attempt to stop the pain, and usually painkillers will prevent them from picking at it.  There really is no way to bandage a rat, they will just pick it off.  Your vet may also glue, stitch, or staple the wound shut if it is open enough, and if he or she does then make sure your rat gets painkillers or she will definitely pick at the wound.

 It's possible that the rat with the wound is scratching at it and opening it up because she has mites or lice and she is itching at them, not her wound.  Treating her with the treatment mentioned above may cause her to scratch at it less and allow her to heal, but if it is infected you will have to get her to the vet anyway.

 I hope this helps, good luck with your rats!