2 mice, one tail shaaking the other loosing fur

Question
QUESTION: Hi,
I have two mice that are less than a year old and have always gotten along really well.
I noticed a while back that one mouse was loosing patches of fur on her face and now on her back. The other randomly shakes her tail. She only does it when she is out on her own and likes to do it near the bars of the cage so it rattles.
I bought them a bigger cage because I thought they might be bored and treated them for lice but still no improvement. I have never seen them fight.
Any ideas?

Thanks,
Andy

ANSWER: Hello Andy,
what type of bedding are you using for your mice? sometimes the bedding can cause fur loss and irritation. please get back to me on the bedding.

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QUESTION: I use dust-free pine litter and I've never seen them sneezing.

Answer
ahhh pine bedding and cedar bedding are known for causing fur loss and liver and  lung disease. Even if the mouse isn't sneezing it sounds like she's having an allergic reaction to the pine and i would take it out asap and use aspen bedding or carefresh or soft-sorbent bedding.