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What flea and tick products are dangerous or toxic for dogs?

Updated On September 23rd, 2025

Pet's info: Dog | German Shepherd | Male | neutered | 110 lbs

What flea and tick medicine has been making dogs I’ll or die

2 Answers

Most Helpful Answer

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Answered By Jennifer Summerfield, DVM CPDT-KA

Veterinarian, Certified Dog Trainer

Published on March 2nd, 2018

I occasionally see toxicity issues with some of the over-the-counter topical flea products like Hartz, Sergeant's, etc. - this is more commonly a problem in cats, but can sometimes be an issue with small dogs as well, especially if they've been dosed above their weight range. All of the prescription flea/tick medications currently on the market (Bravecto, Nexgard, Simparica, etc.) are quite safe and effective.

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    Answered By Lindsey Edwards MVB, BSc, IVCA

    Veterinarian

    Published on June 22nd, 2018

    Most licensed flea and tick treatments are safe when used in accordance with the guidelines - most importantly the species (many cannot be used in cats), age of pet (some are not recommended even at 16weeks), weight of pet and most importantly frequency of reapplication of products used. It is vital to never mix flea products unless clearly marked on the packaging or advised by your vets office - many shampoos, sprays, spot ons and household products comtain very similar ingredients and using multiple products at the same time can rapidly lead to overdose and toxicity. The cheapest product off the shelf is often not the most economical as it may be short or poorly acting, only kill adults on your pets and not repel new infestations or may not control the rehatching of eggs laid in the environment. A good quality household insecticidal spray such as acclaim or indorex is vital to inactivate eggs and prevent hatching and reinfestation. Monthly oral tablets such as capstar or comfortis can achieve rapid kill of adult fleas as they appear or advantix can actually repel as well as kill many biting insects before they feed on your pet. In severe cases, bravecto tablets or seresto collars are recommended and although they appear expensive initially they long duration of action (3 or 8 months) and will continue to control fleas/ticks throughout this period and do not require repeated applications

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