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My dog still has fleas after Comfortis. Why is she still scratching?

Updated On September 23rd, 2025

Pet's info: Dog | Shih Tzu | Female | unspayed | 3 years and 1 month old | 13 lbs

I have a question regarding comforties My dog hasn't stopped scratching after I have her the medication, do you think I should try something else She still has fleas

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2 Answers

Most Helpful Answer

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Answered By Lauren Kennedy, DVM

Veterinarian

Published on August 1st, 2017

Comfortis is a great product and should start killing fleas within 30 minutes. If you are still seeing fleas there are a few things to consider. First, make sure you give the Comfortis on a full stomach and make sure the dog keeps it down (sometimes dogs vomit after taking it). There are also probably fleas in the environment/home. I would recommend vacuuming all carpeted areas in your house and washing all of the pet's bedding. Even with the best flea control it can take up to 2-3 months to get the flea problem under control. Make sure you treat all the other pets in the household as well

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    Answered By Sarah Derksen, DVM

    Veterinarian

    Published on October 4th, 2018

    Hi. The issue is that most likely all stages of the fleas arent being killed at the same time, therefore they keep coming. The other possibility is they are in the environment or on other peta and being reinfected. For a flea infestation you have to treat the pet and the environment by a professional company at the same time! Where there is a live flea, there are a TON of eggs! Good luck

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