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K9 Advantix II Flea & Tick Spot Treatment for Dogs, 21-55 lbs, 6 Doses (6-mos. supply)

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About This Item

Details

  • Helps to protect dogs weighing 21 to 55 pounds from fleas, ticks, mosquitoes, biting flies and lice.
  • Starts working within hours of application.
  • Kills and repels on contact, so fleas don’t have to bite your furbaby to die.
  • Easy-to-apply topical treatment is fragrance-free and waterproof after 24 hours.
  • No prescription needed.

Ingredients

Instructions

Size

FAQ

Learn More About K9 Advantix II From Our Team of Experts

About K9 Advantix II

K9 Advantix II Fights 5 Major Pests

K9 Advantix II protects against fleas, ticks, mosquitoes, biting flies, and lice. It kills fleas on dogs within 12 hours and continues to prevent infestations for 4 weeks. Do not use on cats.

How K9 Advantix II Works

The active ingredients in K9 Advantix II (imidacloprid, permethrin, and pyriproxyfen) spread over the skin. Fleas and ticks are killed through contact, so they don’t have to bite your dog to die.

Flea Treatment & Prevention

K9 Advantix II kills and repels fleas, ticks, and mosquitoes.

Kills & Repels

These flea drops kill adult fleas, flea larvae, and flea eggs to break the flea lifecycle.

Same-Day Effectiveness

K9 Advantix II kills fleas on dogs within 12 hours, and it keeps working for four weeks to prevent reinfestation.

No Prescription Needed

You don’t have to go to the vet to get quality flea and tick protection for your dog—simply buy and apply.

Fragrance-Free

This flea topical formula is fragrance-free and waterproof 24 hours after application.

Frequently Asked Questions

Can I use K9 Advantix II on My Dog?

K9 Advantix II is for dogs 7 weeks of age and older. This product comes in four sizes: Small Dog (4-10 lbs.), Medium Dog (11-20 lbs.), Large Dog (21-55 lbs.), and Extra Large Dog (over 55 lbs.). Choose the right size based on your dog’s weight, and do not use on cats.

How Do I Apply K9 Advantix II?

Break the seal on the tube, then part the hair along the top of your dog’s back and evenly apply the contents from the shoulder down to the base of the tail. The number of application spots will depend on the size and weight of your dog—refer to the product label for detailed instructions.

The Advantage Family

Get the Advantage over fleas with complete flea protection for your pet, home, and yard. The Advantage family of products has everything you need for a complete flea treatment and prevention plan, including monthly topical treatments, pet shampoos and sprays, household sprays for carpets and crevices, and even a yard and premise spray. Just be sure to get the right product for each need and use only as directed.

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Questions & Answers

28 Customer Questions

Does it contain pesticides

How do you apply the topical treatment? Is it messy?

Answer by Chewy • Mar 21, 2024
To apply, remove applicator tube from the package. Use scissors and peel down foil. Hold applicator tube in an upright position and pull the cap off the tube. Turn the cap around and place other end of cap back on tube. Twist cap to break seal, then remove cap from tube. The dog should be standing for easy application. The entire contents of the K9 Advantix II tube should be applied evenly on the top of the back from the shoulder to the base of the tail. At each spot, part the hair until the skin is visible. Place the tip of the tube on the skin and gently squeeze to expel a portion of the solution on the skin. Do not apply an excessive amount of solution at any one spot that could cause some of the solution to run off the side of the dog. Discard the empty tube.

How long do I need to wait before I can cuddle and pet my dog after using K9 Advantix II? How long do I have to wait to bush him and is that fur toxic?

Answer by Chewy • Aug 21, 2019
Once the treatment has been absorbed by the dogs' coat and they're fully dry, normally between 1-5 hours depending on the environment, the treated area should be safe for anyone to touch. It's always recommended to wash your hands after touching your pet.

Does this Kill ticks on contact

Answer by Chewy • Dec 14, 2019
K9 Advantix II kills fleas within 12 hours. New fleas that jump on the dog from the surroundings, such as grass, carpet and pet bedding, are killed within 2 hours with protection against further infestation for at least 4 weeks.
Reviews
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4.5
Rated 4.5 out of 5 stars
4986 Ratings
Terms & Conditions

Customers Mention

Chewy identifies key considerations with the help of artificial intelligence and our veterinarians.

Ease of Use

84% Positive

Effectiveness

84% Positive

Ingredients

81% Positive

Long-Term Benefits

83% Positive

2271 Customer Reviews

Always consult a veterinarian about your pet’s health needs. Customer reviews should not be used as medical advice.

Rated 3 out of 5 stars
By Victoria on Jun 7, 2025

Flea and tick toxicity

My 2 dogs 21 pounds and 25 pounds both got tick and flea toxicity from this product sadly. I think it certainly works , I applied just as directed and both dogs

My 2 dogs 21 pounds and 25 pounds both got tick and flea toxicity from this product sadly. I think it certainly works , I applied just as directed and both dogs are in weight range but it affected them horribly. I had to bathe them 3 times to help their discomfort. Both dogs were acting abnormally a day after receiving treatment one of my dogs face completely swole up . it lasted about 5 days of bad symptoms from both dogs . I’ll attach a photo of the swelling a day after it went down

By Victoria on Jun 7, 2025
Rated 5 out of 5 stars
By Tammy on Jul 15, 2017

Worked perfectly on my puppy. Just two days and there was no more fleas!

My boy is a Siberian and was 5 months old when I found fleas on him. Didn't want him to continue scratching and suffering with those evil fleas I odered this product

My boy is a Siberian and was 5 months old when I found fleas on him. Didn't want him to continue scratching and suffering with those evil fleas I odered this product from Chewy.com, and applied it to him right after it arrived. Two days later, there was no more fleas on him, even when I tried to find if there was any left. There was also no side effects on my boy. It has been almost two months and haven't seen any sign of the fleas coming back yet. Chewy.com has the best price for this product compares to all other pet stores and markets, so I did save some money to get my pup some other goodies. My boy would like to thank Chewy.com for helping him with those parasites and brings great deals for his food, treats, and toys. Love Chewy.com!

By Tammy on Jul 15, 2017
Rated 5 out of 5 stars
By Denise on Jan 22, 2026
  • Bojangles
    BojanglesAustralian Shepherd • 8 yrs
  • Max
    MaxAustralian Shepherd

No more ticks

Our 8y.o. dog & 5 m.o. puppy were getting ticks daily during a warm spell in December. After one application the first week of January the ticks are a thing of

Our 8y.o. dog & 5 m.o. puppy were getting ticks daily during a warm spell in December. After one application the first week of January the ticks are a thing of the past! And our dog and pup have had no bad reaction to this product. I've used it for years on dogs and have never witnessed a bad reaction after using K-9 Advantix II. Also, we have never had a case of fleas. Our dogs enjoy running loose outside where there are plenty of wild critters such as squirrels, rabbits, deer. etc. So our dogs have plenty of ops for picking up fleas & ticks this product also claims to repel mosquitoes which carry heart worms. So glad to note our dogs have never had a case of heart worms . I recommend this product !

By Denise on Jan 22, 2026
Bojangles
BojanglesAustralian Shepherd • 8 yrs
Rated 5 out of 5 stars
By Paula on Sep 23, 2020

Swear by this product

In the past, I tried flea chews, collars which my vet did not recommend, flea shampoos and then I finally tried Advantix ii, and my dog who is now 10, has never

In the past, I tried flea chews, collars which my vet did not recommend, flea shampoos and then I finally tried Advantix ii, and my dog who is now 10, has never had another flea problem. She used to have fleas so bad that she would chew and scratch where she would have fur missing in spots. My vet called it "flea allergies". I do suggest to everyone out there that says it doesn't work, to brush the product through your dog's fur, forward and backward and down to the sides to work the product through. My dog hasn't scratched in years, and she's never had a tick either!

By Paula on Sep 23, 2020
Rated 1 out of 5 stars
By Alexandra on Apr 30, 2025

My dog had kidney failure after using it.

I feel this product led to the passing of my dog. I have no concrete proof however I feel if the dosage amount was closer to my dog weight my dog would still be

I feel this product led to the passing of my dog. I have no concrete proof however I feel if the dosage amount was closer to my dog weight my dog would still be alive. My dog was 20.8 lbs. at time, with a few months ago as high as 21.6 lbs. To ensure she had to proper coverage, I purchased the 21 lbs. to 55 lbs. flea medicine as I thought the 11-20 lbs. pkg was not enough as her weight was closer to 21 lbs. than the 20 lb. marker. She did not show any allergic reaction until the next morning as she would not take her pill with fresh chicken which she adores. The entire day she would not eat anything all day. The following day she just ate fresh grilled chicken which was her very last meal. From then on, she did not want to eat anything at all, not even her favorite chicken. We took her to our vet which did blood work and found out 6 days later she was suffering from kidney failure. We tried doing a kidney wash unfortunately her kidneys were so far damaged that nothing could be done to reverse the damage. Unfortunately, we had to make the decision to say goodbye to her officially 10 days after she took the flea medicine. I feel had a given her the smaller dose she would have been fine. I believe a 55 lb. medicine should not be acceptable to be given to a 21 lb. dog. I really wished I bought another brand that was good just for 23 lbs. and smaller. The vet and the assistants were all trying assure me it was not the flea medicine as the box said it was good for a 21 lb.; but in my gut I believe it was the flea medicine. I’m hoping this message will urge others to really not trust these companies to protect your fur baby. My advice is to get the flea medicine closer to your dog size. I will also be writing a letter to the company in hopes this brand will make another type of dosage in between 21 to 55 lbs., perhaps 21-35 lbs. and 36-55 lb. We first didn’t think it was the flea medicine b/c her symptoms were not immediate. Her only symptom was loss of appetite the following day. She never had any seizures or twitching/scratching. It was only the lack of the appetite the following day which I believe started to affect her kidneys ultimately leading to her death. Since there were no immediate symptoms, it was too late to reverse any damage that already has been done. Too many days went by to recognize she had kidney failure. By then it was too late to save her. I only write this as a word of caution to others to really look at any type of medicine given to your dog. They are counting on you to be their protector. I unfortunately have to live with this pain, but I don’t want her to die in vain without informing others to use caution when buying flea medicine. Please do your homework before giving any medicine on your dog. My prays for all dogs to live a long and healthy life.

By Alexandra on Apr 30, 2025
Rated 5 out of 5 stars
By rsimon99 on Mar 22, 2017

Great product and great price!

I used to buy my flea and tick from the vet every month but it started to get too expensive so after doing some research I found that this seemed to work great,

I used to buy my flea and tick from the vet every month but it started to get too expensive so after doing some research I found that this seemed to work great, so I ordered a two pack to test it out (best price I could find was on chewy). I tried the large on my 21 found 7 month old frenchie and it worked great, no side effects or itching. We take him to the dog park at least twice a week so flea and tick protection is a must for us. I did have a couple of questions about the product so I contacted chewy's customer service and they were great! Once I ran out of the 2 pack I immediately ordered the 6 pack. Will be re-ordering once I'm out!

By rsimon99 on Mar 22, 2017
Rated 5 out of 5 stars
By YodaCorgi on Jun 13, 2017

Great repellent!

Love that it has an option for a 2 pack! I try not to treat with chemicals whenever possible. This year the ticks are really bad so I had no choice, I've been using

Love that it has an option for a 2 pack! I try not to treat with chemicals whenever possible. This year the ticks are really bad so I had no choice, I've been using this for years and it works! When I'm out hiking with my dog I know he is protected against harmful ticks, I never see a tick or a flea on him when using it. He is a corgi and his hair is a bit long so the only drawback is that it makes his hair a bit greasy for a few days after applying it.

By YodaCorgi on Jun 13, 2017
Rated 5 out of 5 stars
By Deborah on Jul 9, 2025

K-9 Advantix II.

I added flea and tick medicine along with my shipment of Taste of the Wild dog food for my dogs. Everything was done professionally. I called in to have it added

I added flea and tick medicine along with my shipment of Taste of the Wild dog food for my dogs. Everything was done professionally. I called in to have it added. They told me what to do how long it would take. I love this company. I have 2 Havanese, Murphy and Boomer. And they're safe and happy with what I order from Chewy. I love this company

By Deborah on Jul 9, 2025
Rated 2 out of 5 stars
By Casey on Jun 16, 2017

2 Weeks That's All You Get

I have four rescue dogs, including two new puppies which I've had now for about a month. When I first applied the Avantix II to them all you could tell it started

I have four rescue dogs, including two new puppies which I've had now for about a month. When I first applied the Avantix II to them all you could tell it started working in just about 10 minutes as the dogs were biting a little bit. The next morning NO FLEAS, I thought how awesome is this. Skeptical (after other guick fixes that don't last) I waited to write this review. Two weeks later the scratching and itching came back. I looked on the packaging which states you can apply it more often than 30 days but I am on disability and a limited budget making reordering impossible. I grabbed my flea comb and started on one of my puppies, you can see the results in the picture. This is just devastating for someone just trying to help.

By Casey on Jun 16, 2017
Rated 3 out of 5 stars
By SadieBaby on May 31, 2017

Have to find the right flea product for my dog ...

Not saying that K9 Advantix isn't a good product, but have enough pet parent experience to know that not every flea and tick medication is the right one for each

Not saying that K9 Advantix isn't a good product, but have enough pet parent experience to know that not every flea and tick medication is the right one for each individual pet and in this instance, it wasn't the appropriate one for my Sadie. She still itched and scratched after application of the medication, so I shall try a different product for her and hope I find one that works better for her quickly. Thanks!!! p.s. ok, ok, ok ... so she's a little spoiled, I prefer to think of it as well loved!!! :-)

By SadieBaby on May 31, 2017