Flea Spot-On Treatments: Why I’m Cautious (Seizures, Rare Fatalities & What Aussie Pet Owners Should Know)

Introduction to flea spot on treatment

Over years in the grooming and animal care industry, I’ve personally seen more dogs react to flea spot-on treatments—including seizures—than the studies suggest. That doesn’t mean every product is “bad,” but it does mean we should go in with eyes open, understand the risks, and know what to do if something seems off. Evidence from regulators and veterinary pharmacovigilance backs up that serious neurological reactions can occur and may be underreported.

1) The risk that’s often downplayed: neurologic reactions

Many popular flea/tick preventatives (especially the isoxazoline class: fluralaner, afoxolaner, sarolaner, lotilaner) carry documented risks of tremors, ataxia, and seizures, even in pets without a prior history. This is why the U.S. FDA issued a class-wide alert to vets and pet owners. Labels and vet advisories now reflect these risks.

In Australia, vets commonly use these products because they’re effective against fleas and ticks, but local vet guidance also acknowledges seizure risk and advises extra caution for seizure-prone pets.

2) “I’ve Seen More Than the Studies Show.” Why That Can Be True

Underreporting is real.

• Veterinary pharmacovigilance agencies (WOAH – Europe, Veterinary Practice journals) highlight that spontaneous adverse event reporting misses many cases, meaning true numbers are underestimated.

Trials vs. the real world.

• Pre-approval studies use small, selected groups of dogs.

• Real-world pets may be on multiple medications, have other health conditions, or be given incorrect doses.

• In Australia, the APVMA relies on post-market reporting (AERP) to detect signals not seen in trials. Reports are often low, which means risks appear “rare” on paper, even if they’re more common in practice.

  Low reporting = less visible risk.

3) Fatalities: rare, but documented

While fatal outcomes are rare, large incident reviews of spot-on products (including non-isoxazoline actives) have recorded pet deaths among reported cases, along with rashes, vomiting, and seizures. U.S. EPA analyses of 2007–2008 data, for example, documented deaths among reported incidents and led to stricter labeling and monitoring. Certain pyrethroid spot-ons (especially when misused, e.g., dog products on cats or co-habiting with freshly treated dogs) are well known to cause tremors and seizures, and have led to severe—and sometimes fatal—poisonings in cats.

Australian and international toxicology reviews detail these risks.

4) What Aussie owners can do (practical, balanced steps)

• Talk to your vet before using any spot-on Ask specifically about seizure history, breed sensitivities, and drug interactions. Vets can suggest non-isoxazoline options for higher-risk pets.

• Use exactly as directed Right dose for the right weight, correct species, correct site, and keep other pets (especially cats) away until dry. Misuse is a major driver of adverse events.

• Watch closely after application. For the first 24–48 hours, monitor for wobbliness, tremors, agitation, or seizures. If any signs appear, contact your vet immediately.

• Report reactions—it truly matters In Australia, report to the APVMA AERP (you or your vet can do this). Better reporting helps regulators spot patterns and update labels or usage advice.

• Consider layered prevention Regular combing, frequent washing of bedding, vacuuming, and yard hygiene reduce reliance on chemicals. For dogs with seizure risk, discuss alternative preventatives and schedules with your vet.

5) My Stance as a Grooming Professional

I’m not against all flea control — parasites cause real harm if left unchecked. But I am cautious, especially with puppies, small breeds, seniors, or dogs with neurological history.

I’ve personally seen seizures first-hand after spot-on treatments, more often than the literature predicts. With underreporting acknowledged internationally and regulatory warnings from the FDA and WOAH, I believe in a risk-aware, vet-guided approach for each dog.

Key Signs of a Possible Adverse Reaction (Seek Vet Help Fast)

• Tremors, twitching, or seizures

• Sudden unsteadiness or collapse

• Extreme agitation, drooling, vomiting, or unusual lethargy

How to Report in Australia (2-Minute Guide)

1. Note the product name, active ingredient, dose, and timing.

2. Record symptoms and when they started.

3. Report to the APVMA AERP (online or via your vet).

   
   

Bottom Line

Spot-on flea products can cause seizures and, in rare cases, death. For most pets, the risk is small — but it’s not zero, and real-world cases are likely underreported.

Partner with your vet, monitor closely after each application, and always report any reaction. By sharing your experience, you’re not just protecting your own dog — you’re helping protect others, too.

6) What I've Witnessed Personally

Beyond the studies and reports, I’ve also seen this firsthand. Over the years, I’ve had friends, clients, and even dogs in my own extended family suffer seizures after being given flea spot-on treatments.

In nearly every case, their veterinarians told the owners the seizures were “just from the dog itself,” not from the treatment. But after speaking with these owners, I suggested they stop the flea spot-on to see if it made a difference.

The results were eye-opening:

• In all but one case, the seizures stopped completely after the treatment was discontinued.

• Some of those dogs are now five years seizure-free without further problems.

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I am not saying this will be the case for every dog — each animal is unique. But what I do wish is that more vets in Australia would openly acknowledge these risks, just as regulators and veterinary bodies in the U.S. are now doing.

My Hope for Pet Owners

My hope in writing this article is simple:

• That pet owners will do their own research.

• That they will feel empowered to question their vet about the potential side effects.

• And that, together, we can create a more open conversation around both the benefits and the risks of flea treatments.

No one wants to see their beloved pet harmed by something that was meant to protect them. By sharing both the science and my real-world experience, I hope more families can make informed, cautious choices for their dogs.

7) A Thought-Provoking Comparison

When humans get head lice or body lice, we only use treatment if an infestation is present. We don’t apply chemical treatments to ourselves every month for the duration of our lives “just in case.”

Yet for our pets, many owners are advised to use flea spot-on treatments year-round, regardless of whether fleas are present or not.

Personally, I only treat my pets for fleas if they actually have them. Combined with regular grooming, clean bedding, and environmental care, I’ve found this approach effective — and it avoids unnecessary chemical exposure.

I’m not saying every pet household will make the same choice, but I believe it’s worth asking:

• Do we really need constant chemical protection, or can we monitor and treat as needed?

• Shouldn’t we, as pet guardians, weigh the real risks of infestation against the real risks of side effects?

Spot-on flea treatment