bald patches on mouse

Question
I have a 15 month old rescued as a baby mouse.  He has never had a skin problem until now. I had poison oak on my arms and he was exposed.  Shortly thereafter he started developing bald spots along one side and on his belly.  Under a magnifying lamp I see no irritation on the exposed skin or evidence of mites--just increasing bald spots. I applied a pet hydracordisone but bald spots continue. He is active and eats well. I use hay bedding and will freeze it first from now on and will sterilize cage. But if I see no irritation on the exposed skin can it be poison oak or coincidentally something else?

Answer
Hi Jeani,

I am so sorry for my late response.  Nothing I have found suggests that mice are sensitive to poison oak, but if he was, I would definitely expect to see irritation, inflammation, or discoloration of the exposed skin.  Additionally, the poison oak reaction should subside over the course of a few days.

Based on this and what you've told me, it sounds like it's simply a coincidence, and something else is going on.  Does he live by himself?  Has he been grooming or scratching more than usual?  Has anything changed recently in his environment?

A veterinarian can examine his skin and tell you in one visit what the cause of the hair loss is, but if a vet is not possible, there are a few things to try.

You've already got some of them down by cleaning the cage and freezing the hay.  Because the areas of hair loss are parts of his body which are easy for him to reach (as opposed to head/neck/shoulders), and because the skin is unbroken and healthy, my best assumption is that the hair loss is a result of overgrooming. Some mice are simply more prone to this behavior, and will trim their hair very, very short (to the level of the skin).  This doesn't hurt them, but is usually a result of some kind of stress.  Is there a new person or pet in the home?  Have you been around more or less?  Have the lights and temperature been remaining on their normal cycles?  Has there been more foot traffic near his cage?  What about ultrasonic noises, like televisions, monitors, etc. that might be left on near his cage?  If you can find out what's stressing him and reduce that stress, you might see an improvement in his coat.

Another thing to try is called environmental enrichment - and it's basically just adding toys and play things to his cage.  Treats, tunnels, jungle gyms, hides, a wheel, soft and safe nesting material, etc. are all great ways to make his home happier and less stressful.  Introduce new toys one at a time and consider cycling them through so that old toys become new again.  Hide treats in the toys so he has puzzles to occupy his mind.  The sky is the limit here - it's basically just you trying to figure out what things make him the happiest.

Of course, a vet to rule out parasites is still a really good idea, but if you don't see any of the following, I would be seriously inclined to think he is just bothered by something and acting out by grooming himself too much.  Things to watch for:

-Redness
-Dry, flaky skin
-Scabs
-Broken skin
-Bleeding
-Pus or any clear or colored discharge
-Bumps/lumps
-Swelling

If you see any of these symptoms and cannot see a vet, please write me back and I will do everything I can to help you narrow it down.

Best of luck to your rescue, and I'm sorry you got poison oak!
-Tam