Fatal food allergies in rats

Running a rat rescue we come across many different illnesses – however, Rosie was a first. When Rosie’s owner telephoned us to say that Rosie (a 15 month old female rescue who we had rehomed had a swollen face, our first thought was that it could be an abscess or even liver problems.

A trip to the vet found nothing wrong and the swelling went down.

Two weeks later Rosie and her two cage mates came to stay with us for a few weeks while their owners went on holiday. We were especially pleased to see Rosie as she was of the few surviving rats from what had turned out to be a sickly bunch of rat kittens that we had taken in when they were just a few days old.

Rosie’s mum, aunt and five sisters had all died prematurely from a whole hot potch of horrible illnesses – respiratory disease, internal tumours, mammary tumours, degenerative disease and two who had died suddenly – foaming from the mouth, swollen tongues – cause unknown.

On the third morning of her stay, Rosie’s face was swollen up really badly – she had huge cheeks that looked like hamster pouches, though seemed fine in her self. The swelling was equal on both sides, so we knew that it was not an abscess. We rushed her to the vets and she was given an anti-inflammatory and anti-allergic drug and we racked our brains as to what had caused such a reaction.

We assumed it was nuts as we’d given her a brazil nut the night before (which the owner had left with us a part of the normal ratty treats) and went home and sterilised her cage and food bowls etc. We then gave her fresh food as this seemed the safest option for her with the plan of reintroducing her normal food stuffs – minus any nuts – over the next few days.

That night Rosie looked normal again, all the swelling had gone and she was fine in herself. As she ran around on the settee I saw her clock a rat chocolate treat on the sofa – I tried to grab it but she beat me to I and stuffed her face with it.

The next day her face was swollen again in the morning which made us think that nuts (and by products such as nut oils) and the small animal chocolates were a possible cause of Rosie’s allergy.

Having spoken that night to a friend who’d rehomed two of Rosie’s sisters that had both died ‘mysteriously’, it all fell in to place. Rosie had been lucky – so far. The two sisters (Mia and Spot) had both had on and off bouts of swelling around the face and times where they seemed like they had something ‘stuck’ in their mouth throughout their lives. But they never showed these symptoms at the same time which would have possibly made a connection that it was something they’d eaten.

The vet had found nothing wrong and then one day Mia started foaming at the mouth, her tongue swelled up and she was dead – all the space of two hours and with the vet administering drugs, too.

The same thing happened with Spot around 4 months later, but without the foaming at the mouth – she’s collapsed and started gasping and by the time she got to the vet, her swollen tongue had literally choked her to death. All this without any warning.

Suddenly it all made sense what was wrong with Rosie – and just how serious ‘a little swelling’ as the owner had put it, can be. We have never personally experienced his before, but what happens is that the face swells up (as Rosie’s did) and depending on the severity of the reaction, so can her tongue, airways etc and/or she can foam at the mouth and she can literally choke to death.

So, what can you do if your rat has a serious allergy like Rosie and her sisters?

First of all it is imperative that your rat is put on a strictly monitored diet and doesn’t come into contact with any foods that may cause a problem.

This means that he or she must not under any circumstance have these foods or even foods that have ‘touched’ what you believe triggers an allergy. Even food that has rubbed against nuts for example can be dangerous to a rat with a nut allergy. Similarly, before picking up your rats, you should wash your hands thoroughly in case you have something residual on them.

Also, it means that any cage mates cannot have these treats either as they may store it in their cage or get it stolen by the rat with the allergy. It may seem ‘mean’ but it is better than your rat dying.

Monitor your rat constantly and keep him or her on the same rat food (don’t mix and match brands in case a new one triggers off an allergy) and feed fresh food plentifully. I know it will be tempting to give him or her a treat – a piece of bread for example – but if you are not 100% sure what is causing the problem this could be fatal.

If your rat shows any signs of having an allergy – maybe they are foaming at the mouth or their face swells up or you can see that their tongue is swollen, you must get him or her taken to the vet immediately for an injection – no matter what time day or night. Leaving it could be fatal.

Your vet will need to inject an anti-inflammatory and anti-allergic drug such as Dexafort which should hopefully calm down any reaction and save your rat’s life.

Whenever your rat has an allergic reaction, to be on the safe side we’d suggest that you completely clean out the cage, change hammocks etc and empty and sterilise the food bowl, water bottle and any toys in case they have come in contact with the substance that is causing the problem.

Line the cage with old towels/t-shirts in case it is something in the bedding (you really have to be strict here as anything could be triggering it off). Feed your rat fresh food only for a few days and then see how they go e goes and gradually reintroduce bedding etc.

I know this sounds all very sombre, but it is so very serious. Rosie has been lucky in that her reactions she has had so far haven’t been bad – however, the next reaction could be the one that kills her.

Finally, if your rat suddenly gets a swollen face but is still acting normally, don’t assume that they are not at risk. Just like children with allergies to nuts, just one brush with the wrong thing and your rat could be dead.


Please note that this article is written from our experience only and should not be taken as a medical diagnosis and treatment. It’s aim is to give information and ideas on what could be wrong with your pet and what your vet can try. Always speak to your vet.