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VETERINARY HEALTH REPORT · UPDATED SEPTEMBER 2026 · 5 MIN READ
The FDA Warning Your Vet May Not Have Mentioned About Flea & Tick Chews

Reviewed by Dr. Emily Hartman, DVM — Holistic Veterinary Medicine  ·  Last updated Sep 2026

In 2018, the FDA issued a rare alert: the class of flea and tick chews recommended for millions of dogs — including Bravecto, NexGard, Simparica, and Credelio — has been linked to seizures, tremors, and loss of coordination. The agency's own fact sheet says these reactions can occur even in dogs with no prior history.

Based on the FDA's 2018 Animal Drug Safety Communication and its isoxazoline fact sheet for pet owners and veterinarians.

This article contains independently sourced reporting and has been medically reviewed for accuracy.

For most dog owners, a monthly flea and tick chew feels like the simple, responsible choice — vet-recommended, easy to give, no mess. But in September 2018, the FDA's Center for Veterinary Medicine took the unusual step of issuing a public alert about an entire class of these products.

The isoxazoline class — which includes Bravecto, Bravecto Plus, Credelio, NexGard, Simparica, and Revolution Plus — has been associated with muscle tremors, loss of coordination (ataxia), and seizures. The FDA's own fact sheet is explicit on a point that surprises most owners: these reactions can occur in dogs with no prior neurological history at all.

"Seizures may occur in animals without a prior history."
— FDA Fact Sheet on Isoxazoline Flea and Tick Products, U.S. Food & Drug Administration
So which dogs are these products not made for?

The FDA's guidance is direct: talk to your vet about your dog's medical history before starting an isoxazoline product — particularly if your dog has ever had a seizure, or comes from a breed with a documented predisposition to epilepsy.

Veterinary research has identified several breeds with meaningfully higher rates of idiopathic (genetic) epilepsy than the general dog population, which sits around 0.6–0.75%: Border Terriers (about 13%), Belgian Shepherds (about 9.5%), plus elevated documented rates in Border Collies, Australian Shepherds, and Bernese Mountain Dogs.

WHAT THE FDA ACTUALLY SAID

2018

Year the FDA issued its isoxazoline safety alert

6

Products named in the FDA's affected drug class (Bravecto, Bravecto Plus, Credelio, NexGard, Simparica, Revolution Plus)

0.6-0.75%

Baseline rate of idiopathic epilepsy in the general dog population

13%

Documented epilepsy rate in Border Terriers — over 17x the baseline

Sources: U.S. FDA Center for Veterinary Medicine (2018 Animal Drug Safety Communication); International Veterinary Epilepsy Task Force, BMC Veterinary Research.

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Disclaimer: The statements on this page have not been evaluated by the Food and Drug Administration. FurSure products are not intended to diagnose, treat, cure, or prevent any disease. Health statistics referenced are drawn from public reporting by the CDC, NYC Department of Health, and academic institutions, and are provided for general awareness only. Some testimonials may include customers who received free products in exchange for their honest review.

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Common questions
Is this FDA warning real?

Yes. In September 2018, the FDA's Center for Veterinary Medicine issued an Animal Drug Safety Communication about isoxazoline-class flea and tick products, based on adverse event reports of muscle tremors, ataxia, and seizures.

Does this mean I should stop using my dog's current flea and tick medication?

No — and neither does the FDA. The agency didn't pull these products from the market. It recommends talking to your vet about your dog's specific history before use. FurSure doesn't replace that conversation — it's a chemical-free option to bring into it, not a substitute for veterinary advice.

Why hasn’t my vet mentioned these risks?

Most vets are aware of the FDA alert, but the manufacturers fund much of veterinary continuing education. There’s also a real tension: chemical treatments do kill parasites effectively, and vets weigh that against adverse event risk. The issue is that pet owners are rarely given the full picture to make an informed choice.

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