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Dog vomiting, diarrhea, panting: heatstroke or flea medicine reaction?

Updated On September 23rd, 2025

Pet's info: Dog | Australian Cattle Dog | Male | unneutered | 1 year and 3 months old | 42 lbs

I gave My 1 yr old Heeler K9 advantics II yesterday morning. weighs roughly 42lbs so I got the 20-55lb flea medication. He threw up this morning but ate normally. I took him on a 50 minute walk around 11 this morning-may have been in the 70s We came back home, he drank water and took a nap. Around 1:30 he was uncomfortable, shaking, and panting. I immediately washed off the K9 advantics flea medicine from yesterday. he then had watery diarrhea. is this heat stroke or a Toxic reaction?

3 Answers

Most Helpful Answer

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Answered By Andrea M. Brodie, DVM

Veterinarian

Published on September 21st, 2018

This is very hard to say. This could be a delayed reaction to the flea preventive, but it could also be heat stroke (especially if he has a fever higher than 103.5F) or it could be just a gastrointestinal problem that happened at the same time by chance. Diarrhea and throwing up can have many causes. It is basically a problem with the stomach and intestines caused by a food over sensitivity, eating something that does not agree with the dog, intestinal parasites, bacterial infection, viral infection, the weather, food change, stress, etc.  I would fast Poseidon for 12 to 24 hours and then put him on bland food for two days, such as boiled white rice and boiled white boneless chicken meat, fed in small quantities over several feeds and then transition back to his regular food slowly over a few days. If this does not clear up the diarrhea or if the vomiting increases, or if he gets lethargic, he needs to see a veterinarian for an exam as there may be something more serious such as an infection going on. If you are very worried about his condition , then you may want to take him to the vet before the weekend.

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Other Answers

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    Answered By Vanessa Yeager DVM MPH

    Veterinarian

    Published on

    Hi and thanks for posting on Petco Pet Education Center, formerly Petcoach! While it is possible this may be a reaction to the K9 Advantix, it may be unlikely since the vomiting and other signs you mentioned occurred 24 hours after application. I would say it is even more unlikely if Poseidon has had this product applied before without any reactions. It is possible Poseidon became a little overheated during the walk but his signs may be related to something completely different as well such as viral, parasitic, or bacterial infection. It is hard to say for sure without examining him first. I would suggest Poseidon see his veterinarian as soon as possible for an exam and evaluation to help determine what the cause is behind his symptoms. Your veterinarian will do a physical exam and may recommend running a fecal testing or blood work to aide in a diagnosis. In the mean time, I'd make sure he has access to cool fresh water and is kept inside out of the heat until you can see your veterinarian. I hope this helps and thanks again for posting!

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    Answered By Dr. Davis

    Veterinarian

    Published on September 21st, 2018

    It certainly could have been a toxic reaction although it is uncommon to have a systemic reaction to the topical Advantix, most reactions consist of skin irritation. If this is the first time you’ve used it then toxicity is more likely than if you’ve applied it regularly without issues. He may have eaten something that upset his stomach too. Unless the humidity was very high and you pushed him heat stroke was probably not the cause. As long as it only lasted a day or so and he’s recovered now then I’m not overly concerned about him at this point. Please take him in for an exam and treatment if he continues to be lethargic or have vomiting and diarrhea. Thanks for using Petco Pet Education Center, formerly Petcoach to help you care for Poseidon.

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