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K9 Advantix II Review 2023: Pros, Cons & Verdict

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By Nicole Cosgrove

K9 Advantix II Review

Our Final Verdict

We give K9 Advantix II a rating of 4.4 out of 5 stars.

Ease of use

Review Summary

Nobody wants to find fleas or ticks on their dog, and not just because they’re creepy, crawly, and gross. Fleas and other parasites carry a wide variety of dangerous illnesses—Lyme disease, Rocky Mountain spotted fever, and ehrlichiosis, to name a few—that can quickly spread throughout your entire household.

Flea and tick preventative treatments are one of the best ways to protect your dog from the discomfort and potential danger of fleas, ticks, and other biting insects. K9 Advantix II is one of the most popular over-the-counter topical treatments currently on the market.

Overall, K9 Advantix II is quite effective against fleas, ticks, lice, mites, and mosquitoes. With proper application, this ointment can safely protect against these parasites for 30 days at a time. Plus, it’s safe to use on most adult dogs (including those who are pregnant or nursing) and puppies as young as seven weeks.

On the other hand, K9 Advantix II works so well because its formula includes several potent insecticides. While most dogs handle these chemicals fine, there are potential side effects that you need to be aware of before use.

Image Product Details
K9 Advantix II K9 Advantix II
  • Prevents new fleas and ticks for 30 days
  • Available for dogs of almost any size
  • Does not require a prescription
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    K9 Advantix II — A Quick Look

    • Prevents new fleas and ticks for 30 days
    • Available for dogs of almost any size
    • Does not require a prescription
    • Kills off existing fleas in just 12 hours
    • Easy to apply at home
    • Safe for puppies 7 weeks and older
    • Potentially toxic to cats and children
    • May cause skin irritation
    • Must be re-applied every month
    • Manufacturer: Bayer Animal Health
    • Treatment type: Topical
    • Species: Dog
    • Breed: All
    • Weight: 4 pounds and over
    • Age: 7 weeks and older
    • Duration: 30 days per dose
    • Doses per pack: 1, 2, 4, 6
    • Effective against: Fleas, flea eggs, flea larvae, mosquitoes, lice, ticks, mites
    • Country of origin: Germany

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    Fast-Acting Defense Against Pests and Parasites

    While K9 Advantix II is billed as a preventative measure for fleas, ticks, and other biting pests, this formula goes one step further. After applying the first dose, you can expect to be rid of existing fleas in just 12 hours. Since K9 Advantix II works through contact with your dog’s coat or skin, new and existing fleas don’t even need to bite your dog to be taken down.

    Depending on the severity of the existing infestation, it might take a little bit longer for K9 Advantix II to get rid of every single flea. But since it targets adults, larvae, and eggs, you won’t need to worry about waiting through an entire life cycle to see the full results!

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    Formulated With 3 Active Ingredients

    Though we believe efficacy is more important than the number when it comes to flea-fighting ingredients, the inclusion of three different active ingredients in K9 Advantix II delivers a well-rounded arsenal against all types of parasites and insects. These ingredients include imidacloprid, permethrin, and pyriproxyfen.

    Imidacloprid is an extremely popular insecticide that targets the nervous system of adult fleas, ticks, and other insects. You’ll also find this ingredient in lawn and garden pesticides, home treatments, and industrial pest-control products.

    Permethrin also affects the nervous system in insects and other pests that either consume or come into physical contact with the substance. While this compound is quite popular for controlling fleas in dogs and livestock, it’s also used in some human-grade products (like anti-lice shampoo).

    While the first two ingredients target adult insects, pyriproxyfen is key in defending against unhatched flea eggs and growing larvae. This chemical acts like a hormone, stopping the insect growth cycle in its tracks. K9 Advantix II would only work against fully-grown fleas without this key ingredient.

    dog scratching
    Image Credit: kobkik, Shutterstock

    Worry-Free Protection for an Entire Month

    Applying sticky, greasy ointment to your dog’s skin definitely isn’t the most pleasant experience. But with K9 Advantix II, you can protect against harmful pests for an entire month with just one minute of work.

    Once each dose of K9 Advantix II fully absorbs into your dog’s skin—about 24 hours after application—your dog can return to its normal routine of rolling around in the yard, jumping in the lake, and getting much-needed baths.

    Not Ideal for All Households

    As pet owners, it’s important to understand the discomfort and health hazards that can come with fleas, ticks, and other parasites calling your dog home. However, the risks of using the wrong preventative medicine can be just as bad.

    The active ingredients in K9 Advantix II can cause dangerous side effects in cats, other small pets, and children who come into contact with the ointment. Ideally, at-risk individuals should be kept away from your dog for up to 24 hours after each dose is applied.

    If keeping other pets and children away from your dog after each treatment isn’t feasible, then Ko Advantix II might not be the best option for flea and tick prevention. Instead, we recommend talking with your vet about safer alternatives.

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    Frequently Asked Questions

    Before you jump into using K9 Advantix II or any flea and tick treatment on your pup, you should know as much as possible about the product’s effectiveness, safety, and any other important details. Here are the questions most frequently asked by customers:

    Is a veterinarian’s prescription required to purchase this product?

    While your veterinarian might recommend or even sell K9 Advantix II, a prescription is not required for this product.

    K9 Advantix II is available as an over-the-counter medication from many pet supplies, farm supplies, and even grocery stores. It is also available online from a variety of retailers.

    dog flea treatment
    Image Credit: goodluz, Shutterstock

    What are the potential side effects of K9 Advantix II?

    Like any medication, K9 Advantix II can cause unpleasant side effects even when used properly. The most common of these include skin irritation, redness, and dryness at the application site. In rare cases, dogs can experience allergic reactions to K9 Advantix II and its ingredients. If you notice such a reaction, we suggest discontinuing use immediately and contacting your vet for alternative treatment options.

    Most side effects of K9 Advantix II are only skin deep, but some dogs can also experience vomiting and diarrhea after application. Serious side effects are normally the result of overdosing.

    Finally, dogs aren’t the only ones who can react to this product. We recommend avoiding direct contact with the ointment during and immediately following each application. Children should also avoid contact with the application site for 24 hours following each dose.

    Is K9 Advantix II safe to use on cats and other pets?

    Dog-specific flea and tick treatments are almost universally toxic to cats and other small mammals, and K9 Advantix II is no exception. All packages of K9 Advantix II even include a warning for cat-owning households: Cats should be kept away from dogs for 24 hours after treatment to prevent dangerous exposure.

    If you’re looking for flea and tick prevention that’s safe for felines, then Bayer’s Advantage II for cats is worth a try.

    Can K9 Advantix II be used on pregnant or nursing dogs?

    Yes. K9 Advantix II is generally safe for use on adult dogs who are pregnant or nursing, as well as puppies 7 weeks or older.

    Since pregnancy and puppy-rearing can be a difficult time for many dogs, we always recommend consulting with your vet before starting any new medications, including K9 Advantix II.

    Puppies with mother on a dog bed
    Image Credit: Tiplyashina Evgeniya, Shutterstock

    Can dogs bathe or swim while using K9 Advantix II?

    Since K9 Advantix II enters your dog’s body shortly after application, it is essentially waterproof. With that said, you should prevent your dog from swimming, bathing, or otherwise getting wet for 24 hours after application.

    After the treatment has been absorbed into the skin, your dog can return to their normal activities.

    How long does unused K9 Advantix II keep in storage?

    Looking at a package of K9 Advantage II, you might notice the absence of an expiration date. Technically, this product does not expire.

    Still, it can lose potency over time. Ingredients may start breaking down 2 years after the manufacturing date (located on each box). Storing K9 Advantix II at room temperature and away from direct sunlight can ensure its shelf life.

    What happens if a dose is skipped or forgotten?

    For full protection, adhering to monthly doses is crucial. Once 30 days have passed since your dog’s last treatment, they will once again become vulnerable to fleas, ticks, mosquitoes, and other pests.

    If you accidentally or purposely skip a dose, the manufacturer recommends applying the next dose as soon as possible. From there, continue applications every 30 days.

    Can K9 Advantix II be used in conjunction with other flea and tick preventatives?

    The answer to this question is entirely dependent on your dog’s individual health and the specific products being used.

    Before combining K9 Advantix II with any other medication, please consult with your veterinarian. Your vet will notify you of any potential interactions or risks associated with using K9 Advantix II alongside other medications.

    K9 Advantix II Extra Large Dog

    What the Users Say

    To round out our review of K9 Advantix II, we felt that it was important to see what real dog owners have to say about this product and its efficacy in real life.

    On the positive side, we found countless reviews stating that K9 Advantix II is the most reliable flea and tick treatment around. This seems to be especially true for large dogs, even those weighing almost 200 pounds! We also found several reviews specifically mentioning how well K9 Advantix II works against mosquitoes.

    But, of course, not all reviews were glowing. After reading through customer reviews, we found two common complaints:

    First, K9 Advantix II has quite a few customer reviews claiming that it made no difference in the presence of fleas, ticks, and other pests. Some of these reviews even came from customers who have happily used the product in the past—it’s unclear whether they received a bad batch or if something else is causing these problems.

    Second and more seriously, we found quite a few owners who reported rashes, gastrointestinal issues, lethargy, and other side effects after using K9 Advantix II on their dogs. While some of these cases may be the result of overdosing, we can’t understate the need for extreme caution when using this and similar flea treatments.

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    Divider 8Conclusion

    After reviewing K9 Advantix II, would we recommend it to the average dog and owner? Yes, we would.

    While K9 Advantix II does come with a few risks, you’ll find similar side effects exist with any effective flea treatment. As long as you take precautions and follow the manufacturer’s instructions exactly, the risks associated with K9 Advantix II are quite low.

    With that said, we encourage owners who have any questions about preventing or killing fleas and ticks to contact their veterinarian. Your vet can offer specific advice and guidance based on your dog’s overall health, weight, and other pets that may live in your household.

    Featured Image Credit: Bayer Animal Health

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