skin problem on mice

Question
hi i was just wondering if you could help me out. i've got a 2 month old female mice whom i got off a friend. she's was really active and healthy in the beginning. however, since a week or two ago i realised that she's getting more subdued each day and then i noticed this bald patch on the top of her head between the ears. Initially i didn't think much of it but now it's getting bigger and the skin's turning a weird shade of greyish/black. upon closer examination i realised that she did still have hair but it was just really thin and short.it also seems to be slightly inflamed. i'm getting really worried as i noticed it's spreading to the area under her ears and i really don't know what i can do to help her.please get back to me asap and hopefully i can get her back to the active healthy self she was before.

ps. i initially thought it was my other female mice who was pulling the hair off her bald patch but i realised that its not the case. in face, even she knows something is wrong with her sister as she cleans the infected spot for her several times a day but i'm guessing the licking really hurts because she'll be squeaking like there's no tomorrow.

Answer
Hair loss is common in old or stressed mice. This could be an allergy reaction but to be certain I would take her to the vet asap. I wouldn't expect a 2 month old mouse to have such problems unless she doesn't get along with the other mouse. However litter sisters shouldn't have problems getting along. It may be a parasite but I would expect the other mouse to be experiencing similar problems.

I'm sorry I can't help further. Your vet should be able to help you. Please feel free to ask any more questions.