mouse with eye infection and now maybe mites

Question
I wrote to you before about my mouse Kit.  She is approx 9 months old and lives with her sister.  In April, she had an eye infection (right eye) and I treated with Terramycin ointment and she was fine.  In mid-May, her left eye became infected and the ointment did no good, so I wrote and was advised to take her to the vets- which I did.  She was put on antibiotics for 10 days and all was fine.  Now, she is scratching her ear and it is a bit red.  I can't find any irritation on the rest of her.  Could this be mites or something else?  Her cage mate is fine.  They live in a habitat made up of 2- 10 gallon fish tanks and a 2 level critter trail cage all conected with tubes.  I clean one section every other day- using mild dish soap and rinsing in very hot water. The plastic tubing is cleaned once a week.  Their food dishes and water bottle are cleaned daily.  As is their exercise wheel.  They have plastic huts and plenty of toys to climb and tunnel in.  I have lots of extras so that they can all be swapped out and cleaned every few days.  I use eco bedding.  They eat mouse/ rat kibble and a small portion of mouse/ rat seed and kibble mix and a small portion of fresh veggies daily.  They each get one cheerio a day for a treat. I had another pair of mice (1 month younger)with the same set up- one of them had asthma and died a few months ago, the other one is just fine.  I guess that I'm just wondering what I am doing wrong- I am new to the world of pet mice.  What should I do about the ear?  I have also noticed a small lump on Kit's neck- it is soft to the touch and appeared over night- so it seemed.  A friend told me it is probably a tumor.  I just love these litter girls and hate seeing them with problems. I have lots of pets- cats, birds, fish , frogs, turtles, and a rabbit. None have contact with the mice, so don't think that is an issue. Thank you for listening and thanks in advance for any advise you have to offer.

Answer
Dear Debbie,

My, you have a lot of pets!  I have mice, a rabbit, and a kitten.  It sounds like you take great care of the mice.  

A vet ought to be able to tell if itching is due to mites or some other problem with a skin sample under a microscope.  Another way is simply to treat for mites, keeping in mind, however, that if it's something else (mange, ringworm) you're losing time.  I would treat for mites, because they are very common, but I want you to know your options.

In the following post I explain how to treat for mites:

http://en.allexperts.com/q/Mice-3824/2009/2/Mouse-mites.htm

You will need to treat both mice and the entire cage at once.

Best of luck

squeaks,
Natasha