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Why is my dog acting strange after taking a flea and tick pill?

Updated On September 23rd, 2025

Pet's info: Dog | Shih Tzu | Male | neutered | 5 years and 11 months old | 16 lbs

I gave Tripp this flea and tick pill that is supposed to be given daily. Ever since he’s been taking the pill, 3-4 day, he’s been acting funny. He’s been acting like he doesn’t want to use the bathroom as in peeing. As far as defacating he used to let me know but he’ll just use it in the house now. He seems to be scratching more and getting out of breath which he’s never done. Also he acts like he has something caught on the side of mouth but it’s nothing. Kinda like he’s twitching in his mouth.

1 Answer

Most Helpful Answer

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Answered By Rodrigo Roca, DVM

Veterinarian

Published on September 26th, 2018

Hello, sorry to hear about Tripp. It sounds like he may be having a reaction to which ever flea medication you are administering. Often, these medications can cause tremors and trembling as a side effect or even when toxic doses are administered. Discontinue the medication, if he improves then he was likely having a side effect, but if his sigs continue or if they get worse (seizures, non-stop shaking and trembling, excessive salivation) then have him seen immediately. Other potential causes may not be associated with the medication and may be a sign of flea allergy dermatitis (allergy to the flea saliva) especially if you have seen fleas on him. Since it is unclear wether his current flea medication is giving him side effects, then your veterinarian may consider using an alternative medication. Hope this helps and best of luck.

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