Do you notice her scratching alot?  It sounds like it could be mites but hard to say.

Deb

Would the other rat possibly be beating up on her at all?  Maybe there was a bit of over-zealous power grooming going on?

Deb

Nope, you won't catch the kind of mites that rats have usually.  There is one type of mite called Sarcoptes that humans can catch.  But that is a pretty rare mite for rats to have.  There are several ways that you can treat for mites -- one that I've heard of is putting about two tablespoons of olive oil on the rat and spreading it over their fur and rubbing it in.  Leave it on because that will smother the mites.  The other way that people use to treat is with Revolution.  Here's a really good website that talks about mites on rats: http://ratguide.com/health/integumentary_skin/ectoparasites.php.  And here's a website with dosage of Revolution: http://ratguide.com/meds/antiinfectives/selamectin_revolution.php.  A rat under one pound of weight would get 0.02 ml applied to the skin between the shoulders.  A rat over one pound would get 0.05 ml applied to that same area.  Make sure to read the link about treating the bedding, cage and area that the rats play in to prevent recontamination.

Deb

Mites are really contagious rat to rat so you would treat both.  It is worth taking both in to the vet to have it checked out as mites generally go for ears, nose and tails first.  The vet will be able to give you the Revolution and dose rate.  Lice is another possibility and a protein allergy the third option.  Revolution will treat mites, lice, fleas and worms.  I have just adopted two rescues who had a bad mite infestation, their previous owner tried the olive oil but it wasn't until the rescue used revolution that they started to heal.

A natural cure for mites (and it realllly works) when the chemicals wouldn't for my rats

One of my rats has gotten mites most all of her life.  I no longer use bedding, except for sheets over towel on the floor--and soft cut up sweatshirt rags for them to carry around and making other bedding spots (it doesn't unravel like towels do).  I disinfected the cage every week or more, I used Ivermectin (but didn't like giving the poison monthly--but tried it, but she still had mites), used the kitten Revolution (didn't like doing that), fed neem leaf powder to them in their food (suppose to get rid of mites and other pests--and DOES totally keep dogs flea and tick free and prevents yeast ear infections on dogs)--but NONE of it ever worked.  She was always still itching and scratching and had scabs on her.  I felt so sorry for her.  The above did keep them "down" so that she didn't get anemic or sick with them, but she was miserable and I was tired of watching her suffer.  Finally, since I use food quality diatomaceous earth to prevent roaches in our house (and it totally works), I decided to take some of it on my fingers--but not a lot as I didn't want to create a cloud of dust that it can do and then cause respiratory problems--so just a tiny bit mashed onto my finger and rub it onto Undot's scabs, back, belly, and privates area.  It is actually good for us when applied and totally kills fleas, bugs, ticks, mites, and other pests.  I did this each day for about a week.  She never got resp problems (because I was careful not to put that much on her)--it is also totally safe and actually good for them and us if they lick it off and eat it--de-worms and has other health benefits, and she has now been free (after 2 years) of mites, itching, and scabs for over 2 months.  YEA--just wanted to pass it on.  But BE CERTAIN you get "food quality" and not the other that is for swimming pools--for the NON-FOOD DE has chemicals that are poisonous added and will kill.  The natural kind is very safe even for eating and is also called fossil flour.  Sherry