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My dog poops more and is itchy after vaccines/flea meds. Is it safe?

Updated On September 23rd, 2025

Pet's info: Dog | Shih Tzu | Male | neutered | 9 years and 6 months old | 12 lbs

My 9 year old Shih Tzu Romeo got all of his annual vaccinations on Thursday, two days ago. He also took Simparica on Friday for fleas. He is itchy which is why they’re treating him for fleas. He seems to be feeling ok but he pooped 4 times today which is out of the daily normal. It’s not Diarrheal. Vet gave me Endosorb in case needed and recommended half a Benadryl. Could the vaccine or flea med cause increased pooping or itchy? Is it safe to give him it if he just got vaccine and flea medicine?

1 Answer

Most Helpful Answer

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Answered By Dr. Melanie, BVSc MS

Veterinarian

Published on August 13th, 2022

Thank you for your question about Romeo. I would not give him the Endosorb since he is not having diarrhea. While I understand being concerned he's pooped more times than usual, sometimes that does happen (it happens with humans as well), and as long as it's not diarrhea, it's a cause for concern. Vaccines can cause diarrhea as a side effect, it can be a common one, flea meds it is not a side effect. Could it be he's eaten more than usual and that's caused the increased pooping? Or had more exercise that usual? If he has fleas, that will be causing the itching. He will need more than one treatment to get rid of all the fleas, and the environment will need to be treated as well, as fleas live in the environment, not on the dog. They jump on the dog to feed, then jump off. It is safe to give him Benadryl if his vet recommended it. I hope this helps!

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