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The Side Effects of Advantage Flea Treatment

 by simone on 07 May 2014 |
57 Comment(s)

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It’s true, honestly Jon Snow you can not stop your beloved pets from fleas and lice simply by wrapping them up in cotton wool… coats that is. Oh brave, handsome, silly Jon Snow.

Luckily for Jon and the rest of us, leading treatment Advantage is readily available. It can be used on dogs, 7 weeks or older, and cats 8 weeks or older, as well as rabbits and ferrets. It is also safe for pregnant and lactating animals. Make sure you talk to your vet if your pet is on medication, if other pesticides are already being used, or if your pet is underweight, elderly or debilitated.

Advantage works as a paralytic to rapidly kill adult fleas and larvae (not the eggs) and therefore breaks the lifecycle of our pets’ most hated foes.

Once applied, the nervous system of fleas and lice is attacked. They are paralysed and die only minutes from coming into contact with Advantage - they don’t even have to bite your pet to be affected. Fleas will stop biting within five minutes of the application, and will be dead within 20 minutes of contact. Advantage kills 98-100% of existing fleas within 12 hours of application and will destroy 99% of flea larvae in the pet's surroundings. 

Advantage is easy to use and remains effective for a month. It is even waterproof so will still work after bathing, swimming, extensive puddle or mud rolling (you know who you are!) or for those wet weather loving, storm chasing pets. 

It is applied through the coat to the dog or cat’s skin and spreads throughout the skin’s oily layer. There are a range of dosages available that depend upon the weight of your pet. Ensure you purchase the correct dosage for your pet and that all directions are followed accurately. Weigh your pet or ask your vet to weigh them - don’t simply guess and apply the dosage you think is correct.

Advantage is an external treatment and must not get into the pet’s eyes or mouth. For small and medium dogs, it is placed out of licking reach on the back between the shoulder blades, and for a cat at the base of the skull. For large dogs over 25kg, the dosage is divided between the shoulder blades, on the back between the hips and at another point in the middle. 

As with any medical treatment, there may be a small portion of animals with individual sensitivities. Always monitor your pet immediately after application and for a few days after. If there are signs of any adverse reaction or if your pet’s health worsens, consult a vet immediately.

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Hair loss and skin irritations
Minor skin irritation is common at the site of application, especially if it is your pet’s first ever treatment. Stiffening or the damp appearance of hair, itchiness, redness or pinkish skin may occur but these are temporary side effects. Occasionally hair loss also occurs. This is usually a one-off and hair will grow back within 1-2 weeks. If the hair loss spreads or doesn’t grow back then consult your vet.

Animals with sensitive skin may develop sores that can bleed if scratched, split or open and then become infected. Check the application site regularly and if these symptoms occur visit your vet. 

Medicinal odour
A low incidence of owners have noticed that their pet has a medicinal-type odour after treatment. This is not dangerous or harmful and will only last a few days to a week after application.


Contact with eyes
If your pet manages to get the treatment in their eyes, flush their eyes immediately with plenty of water and consult with your vet.  

Rare and serious side effects
Serious side effects are rare, usually only occurring in animals with individual sensitivities or allergies to the product’s active ingredients or are a result of accidental ingestion or a mistake in the use of the product.The signs should be noticeable quickly and in all circumstances, immediate veterinary attention is needed if you notice any of the following: 

  • Loss of apetite, increase in thirst, vomiting, diarrhoea or drooling - Remember to apply Advantage as directed, out of reach of your pet’s mouth. The product has a bitter taste that should discourage licking and ingestion. If enough is ingested, it can cause stomach upsets and loss of appetite. Vomiting, diarrhoea, excess salivation, drooling and an increase in thirst indicate excessive ingestion or an adverse reaction.
  • Pupil dilation, eye irritation or increased tear production


  • Breathing difficulties, ataxia (movement problems), stumbling, trembling or seizures


  • Abnormal sleeping, lethargy or non-responsiveness


  • Odd behaviour, depression or hyperactivity

As mentioned, severe reactions are considered to be very rare with Advantage when it is applied as per instructions. As an extra precaution, it is best to observe and separate treated animals for 30-60 minutes to ensure that they do not lick their own application site or that of other animals. Otherwise, Advantage is an extremely easy and effective treatment to make sure your beloved pet doesn’t become high-rise living for fleas and lice. 



Jade  - Comment
Jade 08 Oct 2017Reply
if i feel like my cat is having a reaction, can i wash the area?
Nancy Christie - Comment
Nancy Christie07 Jun 2018Reply
We used Advantage Multi on our otherwise healthy Chesapeake Bay Retruever for flea control. Within 12 hours he was covered with hot spots and within 24 hours he was blind and disoriented. Our vet says to NEVER use this product again. So now what?? My dear dog is now blind. My advice is, if you love your dog dont use this Advantage Multi. It’s poison to more than fleas. Oh and did I mention it causes reproductive issues? So much for my breeding program now. He was the end of a line and now it’s over. No hunting, no swimming. We will learn to work with his blindness. This company needs to stop making this product.
Sarah Peacock - Comment
Sarah Peacock07 Jun 2018Reply
Hi, I am not using Advantage mullti but just Advantage on my dog, do you think this is ok?
Rebecca Smith - Comment
Rebecca Smith13 Jun 2018Reply
I used this on my 1 yr old Siamese cat, never again. He had hair loss at application site. Hair grew back, so gave him a 2nd app months later. He had a severe reaction, drooling, lethargic, jaw tremors. It all happened 4 to 5 days after applying the Advantage II. I was told if I attempt it again, my pecious Mac will die.
Charles Edward - Comment
Charles Edward14 Jun 2018Reply
My chihuahua is having an extreme reaction to advantage multi administered 2 days ago. Eye swelling, ear irritation, head tilting, diarrhea, lethargy, tremors, rapid breathing. This isn’t the first time he’s had a reaction but it’s abaolutly terrifying. I’ll never give any of my dogs including my other two this poison ever again. We are prepared to take him to the emergency vets, called and have everything arranged Incase his breathing turns rapid again tonight. He’s sleeping now and we are praying it will just wear itself off by tomorrow. This product is 100% toxic. Do not believe what anyone tells you, even vets. My poor little buddy is a victim of this toxic marketing ploy. I’ll never give them this crap ever again and I’ll tell every single person I know what it caused my dog to experience.
Do not give advantage multi to any animal, period.
sarh peacock - Comment
sarh peacock14 Jun 2018Reply
What about Advantage, not Advantage multi please? Advantage multi has two ingredients, Advantage only one, Imedacloprid.
Charles - Comment
Charles14 Jun 2018Reply
After our experience we don’t use any of these things on our dogs. Never again.
There are holistic versions made of essential oils we have instead. We will never use these toxic medicines in our dogs ever again. Lesson learned.
Elisabet Sigurdsson - Comment
Elisabet Sigurdsson14 Jun 2018Reply
I applied it to both my dog's just the normal one the terrier is okay but my Bull dog is now having a reaction it's really scary, I won't be using it again
Charles - Comment
Charles14 Jun 2018Reply
Call your vet but ours said we can give a little bit of Benadryl to stop the allergic reaction. Don’t ever use this poison again it’s not necessary!
Louise - Comment
Louise23 Jun 2018Reply
My Binky after advantage is sitting quietly then jumps up runs and hisses I don’t know what to do
Allison Turner - Comment
Allison Turner29 Jun 2018Reply
Advantage dog flea treatment.
Kip - Comment
Kip31 Aug 2018Reply
Advantage II Cat Flea Treatment is dangerous. I used the product on my cat properly....for the correct weight small cat, first application in 5 yrs, indoor cat, no dogs in house to also lick, applied on back of neck, was healthy cat, seperated from other 2 cats till dry. It caused her to have pyriproxyfen poisoning...seizures, partial paralysis from seizures, lethargy, licking, and loss of appetite. The seizures could not be controlled. Note, I also bathed her in mild dish soap when symptoms appeared. I had to put her to sleep. Advantage II manufacturer Bayer would not acknowledge problems but you will find similar cases on the web. Advantage II is not a safe flea treatment option (nor did it work).
TMorga - Comment
TMorga31 Aug 2018Reply
I adopted a new kitty. Put advantage II on her, she has a huge bald spot. This was 4 days ago. I will not use it again.
Brenda - Comment
Brenda31 Aug 2018Reply
Same. Placed it on my cat and next day his fur fell off around medication site. Not using this again!
Juan arenas - Comment
Juan arenas31 Aug 2018Reply
Pésima experiencia con ese producto , le dio alergia a mi mascota, sacudiendo las orejas todo el tiempo, no puede dormir ni comer , le aplicaron un corticoide y no le ha servido , deben prohibir esa porquería.
Susan - Comment
Susan09 Sep 2018Reply
We used advantage on our Jack Russell 4 days ago. She began scratching herself a lot the day I used it but we just thought it was because she had a bath a day before. She has now thrown up 3 times this evening. Her vomit is clear but there seems to be foamy or a cotton like substance at the top of the vomit. It is a Saturday night so our vet is closed and so are all others. We don’t live near a vet that may be open. Can anyone tell me what we might be able to do. Right now she is shaking and shivering. Thank you for any advice you may have. By the way, she is a young 14 year old and we rarely give her flea treatments. We had been working outside all day Monday and she wanted to be outside with us. We noticed she had a couple of fleas when we got in the house. We decided to use it and I wish we hadn’t.
Briana Harden - Comment
Briana Harden16 Sep 2018Reply
I have been looking online to see reviews and or complaints about this product. My rescue BullPei has had this 2x and no more both times he got huge whelps and cyst like in size and scratched himself raw in many places. I was wondering what other products anyone could recommend. Thank you.
Susan I hop your baby is ok and I am sorry that has happened.
Helen webb - Comment
Helen webb28 Sep 2018Reply
My puppy has suffered from seizures since she had started to have the Advantage
Suzanne - Comment
Suzanne29 Sep 2018Reply
My German Shepherd is having a reaction. He's etheric and won't eat and very thirsty. He is my everything! You are selling an unsafe product! I will bring the biggest lawsuit you have ever seen ! My precious boy better be okay..I will never forgive myself for using this! You need to take this off the market now!
Valerie Fry - Comment
Valerie Fry29 Sep 2018Reply
Please tell me your dog is ok now after this incident
Mike - Comment
Mike18 Jan 2019Reply
I used on my cat, "Advantage II", but never again, made the cat crazy, he bit and scratched me. He ran around the house. I called the Vet he told me to wash the cat and watch for foaming of the mouth and seizures. After the washing he seemed to settle down, I do not advise anyone to use this product, it can kill your cat.
Hopecope@aol.com - Comment
How long did this last , my cats are acting crazy
mik - Comment
mik18 Jan 2019Reply
Advantage II made my cats very sick, Vet had me wash the cats and watch to make sure they didn't foam at the mouth or go into convulsions. I am so ashamed I didn't know better, I almost lost my best friends. Do not use this product, it can kill an animal. They did continue to salivate for a while but did settle down. I feel so sick from this, Ill never use anything like this again for fleas. I cant imagine if it had killed my pets how I would feel. I live alone with my 2 best friends, I would die inside if anything happened to "my boys".
Rozena - Comment
Rozena07 Mar 2019Reply
I use Advantage II with my med sized dog and every time we do a treatment she scratches out of control, won’t eat and seems depressed. I’ve been trying to figure out what it was and have now discovered it is the Advantage II topical flea treatment that we just finished (we had the 6 month supply). I feel so bad for her. She doesn’t even have a flea issue when we don’t use it, I just use it to protect her. I’d rather just stop using it and if we notice flea, then treat. This stuff is poison to my dog.
Veronica  - Comment
Veronica 24 Mar 2019Reply
We put Advantage multi on our Beagle puppy this morning. Now his pupils are dilated, excessive drewling, depressed, won't eat and wobbles when he walks around. I feel terrible I don't know what to do. Our vet is closed. When I called they said benadryl and go ahead and give him a bath. Praying he makes it through the night and is ok in the morning. I'm so scared. Any suggestions?
Shirl - Comment
Shirl15 Apr 2019Reply
I used advantage on two of my jack russels. One was 12 and 14. The 12 yr old was my daughters. We noticed a strong smell from the fkea stuff. We tried to wash it off. She started getting really sick and lathargic. She passed withing 7 days of use. She was up and playing then one day took a turn for the worse. We could not figure out what hapoened to her. I used the same batch on my dog a few weeks later. 5 days after use the same thing happen to him. He could not get up. He could not even out his head up. He could not eat . We thought this was the end for him. Its the weekend. No vet. I have been giving him 10 mg bennydryl around the clock. He is now up and walking and eating like nothing happened. Never again will i trust any toxin on my pets. He is highly alergic to fleas. I thought this would help him. We will find another way to deal with the fleas. It only takes 1 flea for him to have a bad reaction. I think 1 flea is better than being posioned. Maybe, this is the new batch they made because fleas are amused to the old batch. Imagine what they had to do to make something that would kill the fleas. Our poor furbabies are guniea pigs.
Dale - Comment
Dale03 Jun 2019Reply
After moving from a state where there are no fleas to California, ( lots of fleas) I used Advantage 2. Within hours my 6 year old cat "Marshmello" showed signs of a severe reaction: watery eyes, nose, and increased salivation. But the worst part was he lost the use of his back legs ! My vet examined him, and after a series of expensive blood tests stated that everyday cats come in with reactions from using advantage 2, and while the drooling and watery eyes would go away the paralysis might be permanent. It's been 3 months now and my cat is still 95% paralyzed in his back legs. Advantage 2 is a dangerous neurotoxin. DO NOT use this product !
Patty - Comment
Patty03 Jun 2019Reply
So sorry to hear about your cat. My cat is having a bad reacion also and I am fearful.
Dalr - Comment
Dalr03 Jun 2019Reply
Patty, I'm so sorry to hear about your fur baby. As for my Marshmallow, after several months, 3 different veterinarians, numerous laboratory tests, $2,000+ in vet bills, he is doing better. the neurotoxins in advantage II caused him irreparable nerve damage, therefore he has been put on phenobarbital to control his seizures. He now has approximately 30% use of his back legs. To control his fleas, we use Comfortis, which is only available by prescription but works wonderfully. Wishing you all the best with your fur baby.
z - Comment
z03 Jun 2019Reply
Hello, I used Advantage II (large cat) on my completely healthy cat 11 year old cat and within the next few days he started showing weakness in his hind legs. Still eating, drinking, etc, and doesn't seem to be in pain, but he was no longer able to jump, his back legs completely collapsed on him a few times and he's walking with a strange wobbly gait in only his hind legs. Took him to the vet where he had extensive bloodwork and x-rays. Everything looked normal. its now been about a month of symptoms. It hadn't occurred to me that it could have been the advantage. Does this sound like what happened to marshmello? thanks in advance for any help-- the only this the vet suggested was further testing such as an MRI which would be extremely expensive
Sheryl - Comment
Sheryl30 Oct 2019Reply
I have been using Advantage Multi on my 2 cats and dog for over 3 months. I couldn’t figure out what suddenly went wrong with my otherwise health felines. My make lost half his fur and my female was lethargic, seemed depressed and was peeing large amounts of blood. $1500 later and nothing is working, I tried another flea medication in between another antibiotic because the advantage didn’t work anyway and suddenly my cats are back to normal. I never would gave thought this was causing it. My mother’s 2 dogs also became deathly ill and 1 almost passed away after applying the Advantage. Never again !
Shanta Swain - Comment
Shanta Swain30 Oct 2019Reply
Sheryl, I’m so sorry you had to experience this. How terrifying. What was the other medication that worked without harm??? Please, I need help for my kids! Thank you!
Jocelyn Gonzalez - Comment
Jocelyn Gonzalez12 Mar 2020Reply
Use por primera vez advantage multi en mis dos gatos, ambos tuvieron reacciones desfavorables, la hembra presentó vómitos, temblores en extremidades, perdida de apetito, desánimo en general dejo de acicalarse y además presentó dificultades para respirar. Mi otro gato un macho presento hiperactividsd y un comportamiento extraño en general. NO LO RECOMIENDO EN ABSOLUTO, POR FAVOR DEJEN DE VENDERLO! ESTAN DAÑANDO A NUESTRAS MASCOTAS
Virginia  - Comment
Virginia 19 Apr 2020Reply
Just adopted a little 5 year old poodle 4 days ago from city adoption site. She was spaded, and given all her medicines including advantage plus all within 9 days. Alot of meds for a 6 pound dog. Today she had 2 seizures, and she walks a little funny. The vet said she thinks the seizures maybe just epilepsy. But when I looked at the meds she received I saw the advantage plus. Never to use this stuff again, it is poison to their system!
Donna - Comment
Donna10 May 2020Reply
I used on my cat last night and right now I'm at an emergency vet as she is trembling and I'm afraid I'm going to lose her 😭
JB - Comment
JB10 May 2020Reply
My cat 13yo has had a severe reaction. She has been in the vets for 3 days and even though she is now eating the tremors and twitching hasn’t stopped 😔 praying we don’t lose her.. Stay away from Advantage it is too dangerous
Sandra Prentiss - Comment
Sandra Prentiss20 May 2020Reply
I just received my advantage II and I wish I would have read these first my cat is pregnant she jumped up and ran then threw up a bunch of foam I am so scared I hurt her and the babies I am crying and so afraid what have I done these are my babies I cannot lose them
Haley - Comment
Haley30 Jul 2020Reply
Okay so if i have a dog and a puppy and I just applied their flea stuff and they go to play.. if one bites the other where the flea stuff is are they gonna be fine or?
froz3nmgirl - Comment
froz3nmgirl15 Aug 2020Reply
I used advantage on my 17 month old bengal and I believe it has made him sick. He became very lethargic, high fever, no appetite. I took him to the vet and all of his lab work came back normal. I have read about advantage causing issues in other pets. I know that he didn't ingest any of the formula. I purchased the 4 pack for large cats as he did weight 12.5 pounds. He has lost some of that weight now.
Serina - Comment
Serina21 Sep 2020Reply
Hello! I just applied the advantage II kitten on one of my kitties and the large cat on two of them. Unfortunately I read these after I applied it but don't feel comfortable with them using it, so I washed off the area with dawn soap within 30 minutes after I applied it, should my cats be okay?
Ashley  - Comment
Ashley 27 Sep 2020Reply
Hi, I work at an animal hospital and im noticing a lot of clients here upset about the medicines they have been giving their pets. I just want to point out that while it IS a risk to put any of these products on your pets, it is no more of a risk individually as us buying medicine to treat our own ailments. Do some research before chosing a flea prevention. All dogs are different, just like people. Some may react terribly and some may have no issues arrise. At my hospital, we have VERY FEW patients who cannot take certain preventatives and we quickly find the solution because without these treatments, these babies can become so infested that it leads to Anemia and often organ failure, followed by death. Ticks can cause a multitude of diseases and disorders as well that also lead to death. To be honest, every day we all do things, take things, and eat things that could potentially kill or harm us. So, while it is terribly unfortunate to hear that some of your babies have had such a horrible experience, I do want to point out that our babies do need some of these options for protection. Please follow the rules and guidelines and watch the precautions. Some medications are better or worse than others. I do believe we, as a race of "intelligence", we could do SO much better for our furry kin.
Freddie - Comment
Freddie27 Sep 2020Reply
My dog has been treated with every. other. treatment. on. the. market. I've worked in pet stores for half a decade, I have unlimited access to every product, and I vet him regularly and have used every prescription product, including sulfur baths. This shampoo, knowing the ludicrous number of complaints, is a last resort.

But I've got 3 acres in the country, and I woke up, walked to the kitchen, and my feet were covered in blood from all the ticks he brought in the house the night before, WITH treatment. He has gotten ehrlichia once, already. I had to try it.

If he has seizures and dies tonight, it will be far more humane than what he has gone through over the past four years with nonstop irritation and organ damage from ineffectual medicines and diseases brought by vermin. I would welcome it as an end to his suffering. But it isn't gonna happen.

Because I also know the public. Especially pet owners. They will crap their own pants and try to shove it in the mouths of anyone who disputes a word of their testimony because ThEy kNoW WhAt'S bEsT fOr ThEiR BaBiEs. They let them eat the polyester filling from a toy and then blame the stomach discomfort on a brand of food the vet recommended.

Every pet owner is a Karen. Ignore the bad reviews.
Gina Baccaro - Comment
Gina Baccaro03 Oct 2020Reply
I put advantage on my healthy 12 year old cat . He developed huge cost like bumps on his neck and he lost fur all around his ears and at the area I applied it to on the back of his neck . I washed him w dawn soap but the damage is done . I feel so horrible for putting that poison on him . Never again . He’s miserable and I feel horrible for doing that to him . I did call a vet and they said 1/2 dose of children’s Benadryl . That seemed to help a little bit . Poor kitty king George . I hope he gets back to normal soon
Alejandra - Comment
Alejandra07 Nov 2020Reply
This is the third time using on one of my kittens and I found this site because I had googled side effects. I think she might of gotten some on her paw and licked a little bit of it. Washed the paw out and am now monitoring her. No big side effects after the first two applications and I have another kitten who also didn't get any side effects with both his applications. After reading all these comments I am freaking out. I've never had an issue with the prior two applications and actually saw a lot of good reviews for advantage II for small cats. Really hoping my baby won't have any major side effects.
Alejandra - Comment
Alejandra07 Nov 2020Reply
UPDATE: washed the area out with mild soap and water and made sure to dry it off. Kitty was fine afterwards. My other cat feel asleep belly up and it dried up on it's own. No side effects both applications on other cat. They are both 7 month old kittens and I used Advantage II for small cats. I don't think I will continue using it although I didn't have major side effects as many people stated here. I will probably look into maybe a flea collar or some other type of flea treatment.
Susan Westerman  - Comment
Susan Westerman 19 Nov 2020Reply
Used advantage on my 15 month old cat 4 days ago ever since she wont go near me she is very edgy and not eating properly she walks around with wide eyes like she's scared hopefully this will wear off and she'll be ok, i wish I knew how this would affect her there should be a warning about how dangerous this treatment is for animals.
Sandra Spring  - Comment
Sandra Spring 23 Nov 2020Reply
I switched to advanced 2 and noticed the next day my cat had diarrhea and it was so bad he couldn’t make it to his liter box now I have him shut in my bathroom now for three weeks and still having accidents but not as bad it’s a good thing I’ve noticed or everything would been ruined so never again on advantage 2!!
Matthew Stark  - Comment
Matthew Stark 03 Feb 2021Reply
Advantage is nasty... period! I've had to use this product because it's effective but it hurts the hell out of my cats. It burns their skin and the fumes from the alcohol content causes them both to squint. I feel like the meanest person in the world for having to use it on them.
They are indoor cats 24/7 but a neighbour in my apartment building allows her indoor/outdoor cat to wander the halls. He sits outside my door daily. I'm at a crossroad. I've tried all natural means and nothing has worked. The manager of the building doesn't care about this matter.
So, if anyone knows of something else that's harmless except to the fleas please inform me.
Anything from Hartz is an absolute no! I'm surprised that they're still still selling their flea collars. As for Bayer, the makers of Advantage, well that's another whole ball of evil.
(If this comment is erased, please know that's its entirety has been screenshot and will post this site, photos, etc., via all forms of media).
Sir Jaq - Comment
Sir Jaq03 Feb 2021Reply
It is horrible what my Jaq has been going through, he was the perfect guy. on June 12 he had is 1st dose of the season and has scratched his neck to the point of bleeding. it is now 3 wks later and he has started scratching and bleeding again. Bathing is Not an option. I feel horrible that i allowed my good boy to be tortured like this!
Why is this garbage on the market. DO NOT SUBJECT UR FUR BABY TO THIS!!!!
Matthew Stark  - Comment
Matthew Stark 03 Feb 2021Reply
My previous comment was definitely not directed to this site. It was pointed at Bayer the makers of Advantage.
I'm very thankful for this site, Petbucket for allow me to express my feelings of anger towards this product.
I get frustrated and write from the top of my head. I should self edit, yes.
Nathan Thomas  - Comment
Nathan Thomas 19 Feb 2021Reply
Hi, I recently put advantage on my 10 1/2 year old cat and he had 5 seizures in the slave of 40 minutes , I took him to the out of hours vets and they gave him an anti allergy injection which helped for 5 days and now today on the 6th day he has had 3 more seizures and idk what to do he’s been to the vets 3 times and is going again tomorrow in just under 14 hours, he is now asleep but since I’ve given him his file treatment he has been drooling from the mouth, he wobbly and then falls on his side and twitches, his breathing is also now heavy. It is so horrible to see and I just want him better, has anyone got any ideas if it isn’t the flea treatment, would be appreciated
Steph - Comment
Steph12 Mar 2021Reply
What if you have two dogs. They play a mouth each other, they will get the others back so what can be done to make this safe? Multi use pills are out due to seizures.
Matt - Comment
Matt03 May 2021Reply
Used the Advantage II for Ferrets on both my ferrets. Never had any reactions or anything. Just like humans that take any medicine, pets taking medicine comes with a risk. Whether that be flea treatment, pain treatment or anything really.
Angelina R. - Comment
Angelina R.16 Jun 2021Reply
Just used Advantage Plus on our Carin terrier X and he has extremely bad chemical burns.
Called the company and was given a case # "in case the vet wants to know the active ingredients " He is miserable, we bathed him in Dawn dish soap then gave him 50mg of Benadryl also but Rx burn cream on the spots and had to put a shirt on him to make him stop scratching the burn spots. I am completely shocked at what this has done to him. There is no recourse if I take him to the Vet it's all on me....Ya I am not happy to say the least. Not sure what else to give him to calm him down and stop the itching.
BeckySue - Comment
BeckySue26 Aug 2021Reply
Cat freaking out. I used it on my siamese cat and within hours she started to have iritic behavior! I am on day 2 of trying to detox her with Chlorine Dioxide (MMS). She sleeps a lot and wants to be very very close to me. Hides under and sheet or blanket she can and twitches one of her ears. Other times she stares at a blank wall w/o blinking. Its like she has completely lost it at times. Never EVER again will I put those chemicals on her body -- that is if she makes it out of this :(
Kat n - Comment
Kat n26 Aug 2021Reply
I used Advantage multi on my 7 year old cat that I got from my vet . A day after she started getting sick didn’t eat or drink water looked really depressed . Took her to pet urgent care . They did a ultrasound and found that her intestines are inflamed . She got some antibiotics and other meds .
Jenna - Comment
Jenna28 Oct 2021Reply
I've used Advantage Spot On for years and my cats have been fine until their latest application. It appears to have turned my cats neck blue!
Luckily he seems to be okay in himself but I can't see anything about this online.
Rather bizzare.
Josh McDowell - Comment
Josh McDowell18 Nov 2021Reply
Vet gave to our 4 month old English bulldog, applied it late last night and 12 hours later he’s in a coma, thought he was just sleeping til I tried to wake him up to feed and he was just limp, then as I tried waking him he’d begin seizing and go limp right away. Currently at the vet but please please avoid this poison. We are sooo upset. Should have researched it but just assumed the vet prescribed it so figured it was safe for a perfectly healthy pup. This shouldn’t be an option for any animal.
Paul Smith - Comment
Paul Smith17 Dec 2021Reply
My cat almost died...still in observation at the vet..he has suffered terrible fits of shaking...cannot walk, crying, fits and total misery. Please don't use Advantage if you love your pet, it's poison, expect nerve damage and kidney failure.
Stefanie  - Comment
Stefanie 03 Jan 2022Reply
This product is horrible
I used this on my 9 year old Jack Russell on Thursday night when I woke up Friday morning he throat was so swollen he has burns on his skin. Hives all over his back and the rest of his skin red raw. I was petrified.
My 8 year old Jack Russell has sores on his skin too and not eaten his dinner since.
I’m so sorry to read all these stories.
I will never ever use it again!
Tracy - Comment
Tracy23 Feb 2022Reply
I administered Advantage multi on my two 3 year old pups and senior dog on Friday night.On Saturday one of the pups was not eating and lethargic. He also had diarrhea. On Sunday, he drank some water and vomited. He seemed to be getting better until I came home from work Monday and he had died. I’ll never use it again.
Carol Barlow  - Comment
Carol Barlow 30 Apr 2022Reply
Hi my vet issued advantage flea treatment for my lop eared 18month old rabbit on Tuesday although he didn’t have fleas he had a very small sore at the side of his eye, he’s a house rabbit, within 18hrs my rabbit started to fall over, I took him straight back to the vet and he said it could be E cuniculi which is fatal, and completely dismissed my concern it could be the flea treatment, we are now in day 3 and he is getting worse, I don’t know what to do, please can anyone give me advise
Lou - Comment
Lou19 Jun 2022Reply
Gave my puppy the correct dosage of advantage flea treatment and 48 hours later he suddenly won't settle to go to bed and has had diarrhoea, he did it in his cage for the first time ever . Wonder if this is a coincidence or a reaction?
Sue Smith - Comment
Sue Smith19 Jun 2022Reply
Take him to the vet, he is having a bad reaction to the medication
Sue Smith - Comment
Sue Smith25 Jun 2022Reply
Gave my mastiff Advantage multi and 5 hours later, he could no longer walk. He is at the emergency vet now- they said he was also partially blind Praying 🙏 that they can save him and get this poison out of him.
Sherry - Comment
Sherry17 Jul 2022Reply
I have used Advantage Multi on both of my cats for three months now and both cats have developed this horrible odor that they did not have before I started using it. One cat is nine years old, the other is three. Has anyone else noticed a smell with their cat?
Erica - Comment
Erica03 Aug 2022Reply
One of my cats started drooling really bad about an hour after treatment, but it only lasted a few minutes and she drank water and it cleared up. I have been monitoring her and she seems to be her normal self since. Another adult male lost his hair and has irritation at the site where Advantag II was applied. Should I not give them Advantage any longer, or maybe for a couple of treatments use the kitten dose even though they are adults?
Mhairi  - Comment
Mhairi 05 Dec 2022Reply
I'm in tears reading all your messages..sounds absolutely horrific!!!
I'm a very lucky owner of 14 beautiful kitties and need to get them all de-fleed and this has been a wake up call for us
I'm lost in what to do after seeing your very sad comments..I hope you're all well and tickity boo and all your kitties and dogs
I'm glad I found this site
Chris cypher - Comment
Chris cypher23 Jan 2023Reply
My 12 year old otherwise healthy cat within hours started vomiting, next day lethargic & won’t eat or drink. Day 2 loss of motor function, stumbling & hissing. Unfortunately it is the weekend & ER vets are far away & too expensive honestly. I am thinking & preparing for the worst. I am heartbroken. He was/is my best friend. So sad big pharmaceutical can get away with this. Pure poison. Watching my pet slowly slip away is torture. I realize this product works for many, but I will certainly seek a homeopathic flea treatment for any future pets I may own. If I ever decide to own another pet. Very angry/sad
Kathleen  - Comment
Kathleen 15 Feb 2023Reply
Does an *unopened* tube of Bayer advantage canine ever $/xpire or lose effectiveness with age
Cindy - Comment
Cindy22 Feb 2023Reply
Advantage II: just administered 3rd application following the summer months to my Siamese. A day later he's scratching and grooming obsessively. A few days later I notice massive hair loss all over his body like hot spots, however, no discoloration nor inflammation. The hair loss continues. The scratching continues - as the fleas are still alive and well! He's evidently having a bad reaction. Never again! Heartz flea collar did the same as the fur around his neck vanished (but grew back)... Collidal Silver in his water to help him through this, whenever that might be. In the future - DE in his food to deworm, perhaps Revolution...Glad I found this site! They need to put serious warnings on their packaging.
Garrett McCabe - Comment
Garrett McCabe12 Jun 2023Reply
I just used Advantage for cats on my pet Polly. Within 10 minutes she started acting unusual, dashing around my house. Polly was foaming at the mouth so excessive salivation. I was extremely worried and tried to round here up for an emergency Vet trip, but the symptoms subsided within five to ten minutes. I have used Advantage in the past without incident, but I guess she has become sensitized. I am researching alternatives.
Pat Byes  - Comment
Pat Byes 10 Nov 2023Reply
I was wondering if this medication can cause dogs to have moles grow on their body in different places.
Andrea Ribera - Comment
Andrea Ribera05 Feb 2024Reply
Advantage killed my cat! My dog is now sick and am praying for God to heal him in Jesus Name!!
Joy - Comment
Joy14 Mar 2024Reply
Advantage caused my shihtzu heart rate to drop.

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