As a dog mom, I’m always on the lookout for flea and tick prevention that actually works. K9 Advantix II is one of those names that’s been around for years, heavily recommended by vets and pet owners alike. It promises to protect dogs from fleas, ticks, mosquitoes, lice, and even biting flies.
Sounds like a dream, right? I placed an order directly on the brand’s Amazon page. It arrived in 2 days, thanks to Amazon Prime perks.
Spoiler alert: It didn’t live up to the hype.
About K9 Advantix II
K9 Advantix II is a topical flea and tick treatment made by Bayer Animal Health, now owned by Elanco. What makes it unique is that it doesn’t just kill fleas and ticks—it also repels mosquitoes and biting flies, which not all products do.
Active Ingredients:
- Imidacloprid (8.8%) – Kills fleas by attacking their nervous system
- Permethrin (44%) – Repels and kills ticks, mosquitoes, and lice
- Pyriproxyfen (0.44%) – An insect growth regulator that stops flea eggs and larvae from developing
Variants by Dog Size:
K9 Advantix II is available in different weight categories, so you need to choose the right one for your dog:
- Small dogs: 4–10 lbs
- Medium dogs: 11–20 lbs
- Large dogs: 21–55 lbs
- Extra-large dogs: Over 55 lbs
I used the Large Dog version (21–55 lbs) since my Lab fits in that weight range.
My experience using K9 Advantix II on my Labrador Retriever
Applying K9 Advantix II is simple; it comes in pre-measured tubes, and you part your dog’s fur between the shoulder blades and squeeze the liquid directly onto the skin. For larger dogs like mine, you’re supposed to apply it in several spots along the back to ensure even coverage. It’s recommended to repeat the dose every 30 days for continuous protection.
The first time I applied it, I expected some immediate relief for my Lab. Sadly, that didn’t happen. Within days, I still noticed fleas crawling on him, and ticks continued to latch on during our walks. I thought maybe I needed to wait a little longer, so I gave it a full month before reapplying. Even after the second dose, the problem persisted.
To be honest, it was disappointing. I’ve always known K9 Advantix II to be a trusted brand, but in my case, it just didn’t deliver. I started wondering if maybe fleas and ticks in my area have developed a resistance to the formula since the product has been on the market for so long. It reminded me of how certain medications lose effectiveness over time, maybe the same thing is happening here.
For context, my dog is a Labrador Retriever, and he has a thick double coat. Even though I applied the product correctly (parting the fur down to the skin), it seemed like the fleas and ticks weren’t affected at all.
Alternative That Worked Better for Us
If K9 Advantix II didn’t work for your dog like it didn’t for mine, here is what worked for us (available on Amazon.com)
Seresto Collar – Here’s the deal: it actually works. It claims to protect against fleas and ticks for up to 8 months, and surprisingly, it kind of delivers. Within a couple days, I noticed way fewer fleas, and ticks? Haven’t seen one since.
What I like:
• Super low-maintenance – You put it on and forget about it (well, mostly).
• No gross smell or sticky stuff – It’s not greasy, and you won’t smell chemicals every time your pet walks by.
• Water-resistant – Bath time or a quick swim doesn’t kill the magic (though too many baths might shorten its life a bit).
• Long-term win – It’s a bit pricey upfront, but if you break it down over 8 months, it’s cheaper than monthly treatments.
A few things to watch out for:
• Skin sensitivity – Some pets might react to it. Mine have been completely fine.
• Not a bug shield – It doesn’t repel fleas and ticks, it just kills them once they make contact.
• Fake products online – Definitely buy from a trusted store (Amazon.com) or your vet. There are some sketchy knockoffs floating around that don’t work (or worse).
Bottom line:
If your pet tolerates wearing it, the Seresto collar is a total game-changer. It saves you time, mess, and gives your pet long-lasting protection. Just keep an eye on them for the first couple days after putting it on, and you’re good to go.
Is K9 Advantix II Safe?
Generally, yes—for dogs. However, it is toxic to cats, so if you have both cats and dogs in your household, you need to be very careful. Never let your cat come into contact with a dog treated with Advantix until the application site is completely dry.
While my dog didn’t experience any side effects from K9 Advantix II, some pet parents have reported:
- Redness or irritation at the application site
- Itching or scratching more than usual
- Lethargy
- Gastrointestinal upset if accidentally ingested
Final Thoughts
K9 Advantix II is a household name in flea and tick prevention, but my experience with my Labrador Retriever wasn’t successful. Despite correct application and repeat doses, fleas and ticks persisted. I can’t say it’s a bad product altogether—many pet parents still swear by it—but in my case, it simply didn’t work.
I personally think fleas and ticks in my region may have developed some resistance to it after so many years on the market. If you’re considering it, just know it may or may not work depending on where you live and your dog’s coat type.
For my Lab, I’ve had much better luck with the Seresto Collar.
While you’re here, read up my review on this pet vitamin called Dog Is Human