Health Problems in Pet Mice

Updated on October 15, 2016


This hub is designed for all pet owners and covers most health problems mice can suffer from. As mice age, their chance of having a health condition increases along with their diet, lifestyle, environment and stress levels. It is important to know that while most simple problems are easily cured with a trip to the vet and some antibiotics, there are some things that cannot be cured. Mice are very tiny, fragile and have a fast metabolism but do not have the same massive immune system as us humans and therefore cannot fight off illnesses efficiently.

You should always remember to thoroughly wash your hands before handling your pet or their food as they can suffer from human illnesses which can become fatal e.g. cold, stomach bug, food poisoning.


Unfortunately tumours are a serious problem in mice. Mice over the age of 1 years are at a much higher risk of developing tumours. Unlike rats, tumours in mice are much less likely to be benign and can turn malignant within 2-3 weeks.


  • Swollen belly on one or both sides. May come on suddenly or over a period of time.
  • A ball like a pea under the skin with no root that can be rolled around.
  • A swelling or lump on any part of the fur that can be moved.
  • Weight loss.
  • Being hunched, lethargic or waddling.
  • Blood from the genital area.
  • Head tilt or loss of balance and problems walking.

In younger mice, tumours can be remove through surgery at your local vets. The surgery can be risky but it usually has a good outlook. Unfortunately the majority of the time the tumours will come back but surgery can add a couple more months onto their lifespan. If the tumour has not returned within 3 months, your mouse may be lucky and it won't return at all. A vet is very unlikely to remove a tumour in an older mouse and will advise the best course of action. Mammary tumours are by far the most common.

A lump does not always mean a tumour, especially if the mouse lives with other mice. It could be a cyst, abscess or injury.


Thankfully not all lumps mean your mouse has a cancerous tumour. In younger mice or mice with cage mates sometimes a lump can be an abscess. These are caused most often by bites that have become swollen and infected.


  • A swollen ball when felt has a root or stem under it and cannot be rolled around much.
  • A scab, cut or pus leaking from a wound.
  • A swollen but squashy area of skin.
  • Fluid draining from the infected area.
  • When a vet attempts to drain, fluid comes out.
  • Mouse may continuously groom, bite at or rub the area through discomfort.

These are very treatable usually with antibiotics and fluid draining. You should always take your mouse to the vet for proper diagnosis as an abscess doesn't have to have a cut area, but most commonly they do have some kind of skin lesion.

Mites, fleas, ticks.

These are also a fairly common problem for mice, especially ones that are kept around other pets. Mites, fleas and ticks can cause excessive scratching, skin irritation, baldness and even in some cases skin infections. They are very distressing and annoying to your pet and can be treated at the vets or using a suitable home treatment for mice and small rodents that cures these insects.


  • Small black spots or bugs on the skin.
  • Flaking or scaly skin.
  • Baldness from scratching.
  • Excessive scratching, grooming, rubbing or obvious physical discomfort.
  • Scabby skin, especially around the ears and legs.
  • Small insects on the fur.
  • An obvious tick attached to the skin.

Most of the time it is just a simple case of mites which can be cleared up easily. Make sure you thoroughly read packaging or have your vet administer treatment. You can prevent this entirely by only using high quality wood shavings and bedding that have been tightly or vacuum-packed and purchased from reputable store shelves rather than farms, barns, etc. If you are worried, you can freeze shavings/hay for 24 hours or put them in a very cold temperature before giving them to a pet to kill any potential bugs inside. Never use shavings you have found on the floor or from a sawmill that have been taken from the ground, they could be contaminated or toxic. Don't allow your mouse into contact with wild mice, let them loose outside or allow other pets to touch them.

Wet Tail.

This is a very serious illness that mostly affects hamsters, however, mice are no exception and can also suffer from wet tail. Wet tail is a serious intestinal disease that is caused by stress. An overgrowth of bacteria in the gut causes watery diarrhoea with a foul odour that can become fatal within hours. There is NO home remedy and it can only be treated from a vet.


  • A foul smell coming from the cage or smelly diarrhoea.
  • Ruffled coat and dull eyes.
  • Waddling or weakness of limbs.
  • Loss of appetite and animal not drinking.
  • Mouse sleeps a lot and becomes much less active.
  • Dirty/wet bottom - usually brown or black in colour.

As I said before, the ONLY way to treat it is through antibiotics from a vet. You must take your animal immediately for treatment as there is no home treatment available and it does NOT get better on its own. You can prevent wet tail by always keeping the cage clean, keeping the room quiet and comfortable and keeping stress levels as low as possible. It is more common in hamsters under 12 weeks and younger mice.

Uterine Problems.

Uterine problems only occur in female mice as males do not have uterus (womb). These problems are more common in older females, especially ones that have been used for breeding or have had babies too young/old.


  • Bleeding from the genital area.
  • A gooey or smelly discharge around the genitals.
  • Swollen belly.
  • Constantly damp underneath.
  • Ruffled coat, loss of activity.
  • Waddling or problems walking.
  • Incontinence.
  • Protrusion from the genital region e.g. something "sticking out"

It is very important to know that only a vet can diagnose and treat these conditions. In some cases it is just infection which can be cleared up in a few days with antibiotics. In others it could be birthing difficulties if your mouse is/was pregnant, problems after the birth or even an internal tumour. In the case of a tumour there is very little that can be done. To prevent this issue, please do not breed your mice.

Urinary Tract Infection.

More common in older mice (1year+) and especially in females. However this can happen to either sex and can eventually become a serious issue. UTIs are caused when bacteria enters the urethra or grows inside the bladder. This is not usually a problem for mice kept in clean conditions all their lives with good health.


  • Smelly or dark/discoloured urine.
  • Blood in the urine.
  • Squeaking or crying when going to the toilet.
  • Incontinence.
  • Being wet with urine that is yellow or brown underneath.
  • Increased drinking.

UTIs are treatable only with antibiotics and should be caught ASAP to prevent them spreading to the kidneys or turning to pneumonia. In most cases they are not serious and clear up after treatment within a few days. Your mouse is likely in a lot of discomfort.

Sticky Eyes.

There are two conditions. One being red tears which can be mistaken for blood but are actually caused by stress and are harmless. These resolve themselves within a couple of days. The second issue is conjunctivitis or allergy.


  • Gooey or sticky eyes.
  • Gunge around the eyes.
  • Eyes are sealed partially or fully shut.
  • Ruffled coat, hunched position or seems unwell.
  • Sneezing, coughing or watery nose/ears.

Most of the time this is not serious and improves after being bathed with a gentle cotton swab and having the bedding changed to something else. Use dust-free shavings rather than sawdust and make sure all surfaces are wiped down and no chemical cleaning residue is left behind. You can take your pet to the vets for eye drops or antibiotics if infection is present.


Fighting, being dropped, being squashed, poorly handled, or accidental toy injury are all problems that mice can face. Fighting between males is the most common cause of injuries with poor handling being second and injury from toys being third.

You should not ever keep two males together as they will fight to the death, once blood is drawn they should be parted and never put back together again. Females can live happily in pairs or small groups without any fighting.

Avoid using wheels with grating or open slats. These are very dangerous as little legs, tails or necks can be trapped and snapped in them as well as being caught and toes pulled off or cuts. Always use flat plastic toys, saucer wheels or sealed plastic wheels to prevent injury and make sure any other toys given are safe for mice, fitted securely to the cage or you follow all directions properly.

You can lift a mouse gently but firmly using the root of their tail and a hand underneath to steady them. Always cup them properly and hold over a soft surface against your body. Never let go of a mouth that is frightened or bites you and don't allow untamed pets to run around on your shoulder as they can easily fall off and get hurt. Never pull a mouse off of cage bars or when they are gripping something as you can pull the skin off their bones or cause them serious pain. Mice do not make good pets for children.

Cage Rage.

A genuine mental health disorder that affects any animal kept in a cage. It is most common in hamsters, but mice can suffer too. It is caused by being kept in a cage that is overcrowded or too small. The animal will likely be suffering emotionally and through physical health problems. Mice of any age can be affected.


  • Frenzied bar biting or continuous biting even after being fed, played with, etc.
  • Damaged teeth as a result of toy/bar chewing.
  • Destroying of personal objects e.g. toys.
  • Racing around the cage.
  • Excessive marking of territory.
  • Aggression towards humans who try to open the cage, clean them out or feed them.
  • Attacking cage mates unprovoked.
  • Guarding cage opening and trying to bite you.
  • Becomes difficult to handle, starts biting or showing signs of aggression.
  • Animal is very possessive and protective over their things - like when they have babies.

Fortunately this is usually fully treatable and improves after the animal(s) are moved into a larger cage. Please buy cages that are plenty big enough for your pets so they have lots of space to run around, play and have fun. This is a completely preventable issue. Allowing the mouse out to play, handling them and giving them plenty of exciting toys can completely resolve the problem within a few days.

Upper Respiratory Infection (URI)

This is another common problem with any small animal and is caused usually by dirty living conditions or a dusty environment. It is a preventable problem and can affect a mouse of any age or gender but is slightly more common in older mice.


  • Coughing, wheezing.
  • Watery eyes, nose, ears.
  • Sticky or sealed eyes.
  • Mouse may be clicking, ticking or making another unusual noise.
  • Difficulty breathing, heaving sides or gasping for breath.
  • Discharge from the mouth.
  • Ruffled coat.

This needs to be treated ASAP and should be an emergency. Only a vet can give you the correct antibiotics to treat your little friend. This can become fatal in hours. Make sure you use dust-free wood shavings rather than sawdust, never use pine or cedar or scented shavings. Make sure you clean your pet out at least once per week to prevent filth and mould from accumulating in the cage.


Allergies can be a common problem in mice and are usually caused by poor quality or scented bedding. You should always use dust-free wood shavings and never sawdust. Avoid anything that contains pine or cedar as these have toxic phenols which can make your pet seriously ill. Avoid anything "Scented" such as lavender or lemon which help prevent bad smells, these are also unhealthy and cause reactions or illness. If you're using hay, freeze it first and buy timothy hay which comes in many brands and is dust-free and good quality. Vacuum packed hay from pet shops is the best option. Allergies can also be caused by certain foods, cleaning fluids, candles burning and even to pollen.


  • Sneezing, coughing or breathing problems.
  • Scratching or excessive grooming.
  • Watery eyes.
  • Discharge from the nose or ears.
  • Itchy ears.
  • Inflamed or red skin.
  • Greasy fur.


As mice become old they can lose their eyesight a little or entirely. It is not uncommon for elderly mice to suffer from sticky eyes, dry eyes, watery eyes or eyes that seal shut with no symptoms of infection. They will usually release again after gently bathing with a cotton swab and warm water. Never submerge your pet in water!

Blindness can occur with cataracts, milky eyes, through infection, trauma or old age.

Unfortunately for a blind pet there is nothing that can be done to salvage the eyesight. As long as your mouse has quality of life they can live happily without problems.


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    • profile image

      Kristoffer Huber 

      6 days ago

      Hi, I’m a 11 and I’m concerned about my female mouse Smokey. Smokey has the symptoms of the URI and has symptoms of allergies, so I don’t know how severe her condition is. I am praying to God that it is just allergies, but I can’t be sure if my Mom and I should head to the Vet or not, but we are trying to “sterilize” the cage. Smokey is about 7-8 months old and lives with her pal Jewel, another female mouse. They live in 2 combined KritterTrail mouse cages and are given fresh food and “gourmet” grain+water regularly. Are we doing something wrong? Or do we need to continue on with our process? Please someone tell me what is wrong with my poor mouse, it is breaking my heart to have to see her like this.......

    • profile image


      6 weeks ago

      My mouse suddnly became really hyper, he has been running on the wheel for 5 hourse with barly any rest, and that is coz i gave him fresh food to try to make keep calm. He usually quiet and slow... now its like he is on something. I didnt change his diet or nothing, he got a giant cage to himself and lots of toys. He sometimes gets out of the cage to play in a the house but he preffers to stay in his cage most of the time. Does someone know what is going on with him? Its 4am and he wont let me sleep... im really worried!

    • profile image


      7 weeks ago

      Check on my male mouse this morning and his testicles were huge and inflamed looking is that bar or normal

    • profile image

      Mistchife the mouse 

      7 weeks ago

      I have a pet mouse with a cyst like thing on her that seems to itch and has bled before from her itching it, its right where her armpit would be but out of the way so she walks fine, i am woried and dont know what to do, i dont have the money to take her to the vet

    • profile image


      2 months ago

      I've discovered some white hard/ crusty stuff around my mouses head along with loss of fur in that are any ideas

    • profile image


      2 months ago

      My mouse has a slightly red limp on the side of her face and isn’t massive but it’s kind of big compared to her head, can anyone help? X

    • profile image


      2 months ago

      My mouse just has dry skin, I've tried looking for fleas or tick or bugs but there is nothing.

    • profile image


      3 months ago

      I haven't heard or seen my mouse eat of drink for a couple days

    • profile image


      3 months ago

      My mouse's eye is swollen and has pus on it.

    • profile image


      3 months ago

      I have 3 mice but one of them doesn’t live with the others because we are still in the bonding process. I check my mice everyday and today I saw weird white spots/bumps on my Moises ears. I tried to search up what is was, it had no answers. Is there anything wrong with my mouse?

    • profile image

      Afrin hussain 

      3 months ago

      I have a white mouse ... his neck Is swelling day by day and he is bleeding from nose...

    • profile image

      valentina mazzarese 

      3 months ago

      we have three white mice, and all of a sudden, one of them became huge, getting really fat. then, her eyes began to get dull, and they are only half as bright red as all the others. they are more orange. she sleeps all night and day, and when i got her out, she wasn't moving in my hand. whats wrong with her and what should I do?

    • profile image


      4 months ago

      go to the vet!!!!!!!

    • profile image


      4 months ago

      My mouse Oreos fur is scruffy and shes hunched and eats but doesn't drink. Shes bout to die please I don't know Whts wrong;(

    • profile image


      5 months ago

      My mouse somehow got a hole in his ear. It’s not bloody but his ear is red. He’s a one year old feeder mouse. He lives in. A ten gallon tank by himself. He doesn’t seem to be in any pain but I’m still worried

    • profile image


      8 months ago

      My pet mouse, Lucy, has been acting weird lately. Her front and back left paws are limp and she usually drags her hind one. Her left eye is almost always half-closed, and she wobbles around and has trouble getting up. I tried feeding her food, but she wouldn't take it. I think she might have low blood sugar, but if anyone had any other ideas, please tell me! Lucy is a female fancy mouse and she is almost a year old. Only today has she started to act this way (November 28, 2017). Yesterday she was perfectly fine. I use Carefresh for her bedding and Vitalsmart food (the only food she eats) for her. I had tried to give her a more 'healthy' food mix by mixing Vitalsmart with National Geographic brand. I switched back to only Vitalsmart after Lucy started acting this way. She is very dehydrated and is getting stronger, all I hope for is that she's going to be okay.

    • profile image


      9 months ago

      My mouse has tiny dots like goosebumps on his back, and sometimes area around his genital is wet with urine. What should I do? I'm really worried

    • profile image

      Snowflake............ Echo.......,..... 

      10 months ago

      My new mouse named Echo has gotten out of her cage at least a one fourth of the time I've had her. Today I found her under my bed and she would usually run away by the time I tried to get her since I only got her eight days ago. This time she just laid there limp and only ran about an inch when I tried to get her. Since then I have noticed that she has just stayed is the same corner, not trying to sleep in her igloo or anything and only tried to get water once and couldn't. It's been about eight hours and she hasn't moved positions. know that she might just be tired from all the running around, but I'm worried that its more than that since she can't really move and won't try to eat or drink. Dose anyone know what's wrong with my Echo?

    • profile image

      Clover the mouse 

      11 months ago

      My mouse, clover is not looking so great. She seems very skinny. This is not definite, but it looks like her eyes are closed and won't open. She is eating, and I am trying to get her to drink water. When she walks around d she sort of tilts sideways, and I have to help her get up. After she finished eating some sliced up carrots, she tried walking back to her hide, but fell. I had to pick her up (she was very light) and put her near the hide. She is also loosing hair on her head and a bit by her head, but on her back. She has a hunched up back. Please I do not know what is wrong, but I am really worried! Please help!

    • profile image


      12 months ago

      I had two pet mice but one died. It had a hunched back, trouble walking, diarrhoea, slept a lot more than I used to, didn't drink as regularly and had a ruffled coat. We still have the other mouse but it seems to be suffering a lot the symptoms. We are worried that the other mouse will die too! We took the (now) dead mouse to the vet and she said we couldn't do anything about it, but we want to try and save the last mouse. Is there something you think we can help it with to prevent it from dieing?


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