My guinea pig has allergies. When will Benadryl work & for how long?
Thanks for your question about Oliver, and I am sorry that he is having some respiratory issues. If he has allergies and is being treated with the diphenhydramine regularly, you should see some sort of improvement within a week of being on it. As far as your question about whether life-long treatment will be required, that would depend on whether you and your veterinarian could identify the item (or items) that Oliver is allergic to. If that can be identified and eliminated from the environment, then you may not need constant treatment. It may then only be required on an as needed basis.
If you do not see improvement on the diphenhydramine, then I would agree with your veterinarian that radiographs (x-rays) would be needed. Unfortunately, pneumonia and other lung issues are very common in guinea pigs, and this would show up on the radiographs. If that is seen, your veterinarian would likely need to change up the treatments that have been tried in Oliver before.
I hope that gives you a place to start, and that Oliver feels better soon.
Updated on September 23, 2025