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What is Advantage Flea Medication Allergy?

Advantage flea treatment is made by the company Bayer, and its active ingredient is imidacloprid. Imidacloprid is an effective and typically safe-to-use insecticide that kills fleas. Although it is considered safe to use, this active ingredient can cause adverse reactions by cats. 

This monthly treatment should not be used on cats younger than 7 months of age and should only be used by carefully following the instructions. It is to be applied between the shoulder blades of the back and you should only use the specific dosage according to your cat’s weight. 

The ingredient, imidacloprid, affects the nervous system of the fleas and paralyzes them. The fleas eventually die within twelve hours. Within just five minutes of applying Advantage, the fleas stop biting and the larvae are killed. This waterproof treatment lasts for about one month, and then needs to be reapplied. 

Many cat owners use Advantage flea medication because it is considered safe and effective. Other benefits of this medication are it is inexpensive, easy to use, and readily available in many stores.

Advantage flea medication is commonly used to rid cats of fleas and is considered safe. However, some cats develop an allergy to the medication, and if this occurs, it is important to contact your veterinarian.

Symptoms of Advantage Flea Medication Allergy in Cats

If your cat licks any of the product or has an adverse reaction to the skin, he will exhibit the following symptoms. Symptoms of Advantage flea treatment allergy in cats include:

  • Drooling
  • Vomiting
  • Diarrhea
  • Irritation of the skin
  • Shaking of the head
  • Seizures
  • Loss of appetite
  • Lethargy
  • Difficulty breathing
  • Itching
  • Biting at the skin


There are many types of safe flea treatments available on the market today; however they can still cause a reaction if not used properly or if your cat is allergic. Other types of active ingredients in flea medications include:

  • Selamectin
  • Fipronil
  • Methoprene

Causes of Advantage Flea Medication Allergy in Cats

Advantage flea treatment is known to be safe for cats; however, some cats may develop a reaction to the active ingredient. Causes of a reaction include:

  • The medication is absorbed through the skin
  • The medication can enter the cat’s bloodstream
  • The active ingredient can cause nerve damage
  • The cat may suffer from an accidental overdose

Diagnosis of Advantage Flea Medication Allergy in Cats

If you suspect that your cat is having a reaction to his Advantage flea medication, contact your veterinarian. Take the container and packaging to the appointment with you so your veterinarian can be sure of what is giving your cat problems. Your veterinarian will ask you questions about the type of medication he is on to help fight his fleas. He will then take a closer look at his symptoms and gather information about them, such as when they began and the severity. 

The veterinarian may thoroughly wash and rinse your dog to remove any of the treatment and begin giving him fluids to help with hydration and to stabilize his symptoms. He will take blood work, urinalysis, and a biochemistry profile. The blood testing will focus on your feline’s serum levels. Although blood testing and urine testing are not always absolute, your veterinarian will be able to rule out other illnesses by taking a close look at your cat’s symptoms and having the knowledge that he began having a reaction after the application of the product.

Treatment of Advantage Flea Medication Allergy in Cats

Unfortunately, there is no treatment for imidacloprid toxicity. Your veterinarian will explain to you what you can do at home, and will treat his symptoms. Treatment methods may include:


Your veterinarian may have already washed and thoroughly rinsed your cat to help rid his skin and fur of the toxic ingredient.

Avoid Exposure

Your veterinarian will suggest to you that you avoid all further applications of the medication. He may also suggest holistic methods to help control and get rid of fleas.

Gastric Lavage

For severe cases of poisoning, such as if your cat has ingested the medication, your veterinarian may perform gastric lavage to help rid his stomach contents of the medication. This treatment method will be followed up with a dosage of activated charcoal and possibly a dosage of laxatives.


Your veterinarian may want to keep your cat for a day or two and monitor his progress as he is on IV fluids. The fluids will help your cat remain hydrated and help further flush out any toxins.

Recovery of Advantage Flea Medication Allergy in Cats

Most cats have an allergic reaction if they were given too much of the product or if they ingested a specific amount of the medication. Your veterinarian will communicate with you about your cat’s prognosis. Once you take your cat home, continue to monitor him for any other side effects or reactions. Be sure to give him plenty of fresh water during the day and night and monitor his drinking and urination habits. 

In order to avoid this from occurring again, you may want to consider holistic remedies to help control fleas. You can talk to your veterinarian about the types that are available to help your cat during peak flea seasons. If you have any questions about the main ingredients of products that can be used to help fight fleas, ask your veterinarian.

Advantage Flea Medication Allergy Questions and Advice from Veterinary Professionals

domestic short hair
1.5 year
Mild condition
0 found helpful
Mild condition

My cat Lily is 1 and 1/2 year old. She recently got fleas coz she goes out even though thts only for short times but many times in a day. I applied advantage ll last Friday like 7 days ago and she still has 1 or 2 semi dead fleas that she is dropping here and there. Also she started scratching only her neck and head but not right after advantage. Thts like 3-4 days ago and she still goes out but I limited it which she is not liking. When she had fleas and I didn't apply anything she was scratching all over her body. Now only head and neck and I'm sad to see her like this. I m thinking to give her bath but I'm scared of that Medication might wash away? Kindly help me

Dr. Callum Turner, DVM
1680 Recommendations
You can wash Lily without worrying about the medication, once it is dry you can bathe her without any concerns about washing any the medication as it soaks into the skin and doesn’t remain on the skin. Give Lily a good bath with a flea shampoo and spray all surfaces like beds, sofas and other fabric surfaces with a fipronil spray to treat the environment and wash bedding etc… on a high temperature wash. Regards Dr Callum Turner DVM

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Mixed Russian Blue
8 Years
Mild condition
0 found helpful
Mild condition

Has Symptoms

Itching, redness

y cat had an allergic reaction (redness, itching, sores on neck) to a %Seresto Flea collar by Bayer. The active ingredients in the collar are Flumethrin 4.5% and Imidacloprid 10.0%. Is it safe to use Bayer Defense Care Flea Protection topical treatment, with the active ingredient of Imidacloprid 9.1% on her?

Dr. Callum Turner, DVM
1680 Recommendations
Firstly bathe Bella to remove any possible residue left from the flea collar; I would leave her without any flea treatment for a week or two before trying another flea control product. We do not know what the underlying cause of the allergic reaction was, whether it was due to the collar’s active ingredients or another constituent of the collar. I would try using a different active ingredient for the next flea treatment (like fipronil) to see if there is any reaction. Regards Dr Callum Turner DVM

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Maine Coon
14 Weeks
Mild condition
0 found helpful
Mild condition

Has Symptoms


Hi I gave my 14 week kitten a 4x advantage spot on flea treatment which the Breeder gave me & she has been extremely lathargic now for 2 days , sleeping all day and night only moving to eat & drink & to use the litter tray

Dr. Callum Turner, DVM
1680 Recommendations
I may not be sully understanding your post but did you put all four pipettes from the box on to Delilah? if so visit your Veterinarian or Emergency Veterinarian immediately as one pipette is one month’s treatment. With normal usage, lethargy may be a side effect of administration and it is usually a case that you need to wait for the medication to leave her system; for next month discuss an alternative with your Veterinarian. Regards Dr Callum Turner DVM

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9 Years
Has Symptoms
Lethargic, Lessened Appetite, Some Difficulty With
Loss Of Balance
Actually this happened 2 times. I didnt figure out it might be a reaction until the second time. 1st she quit eating, got dehydrated(possibly from diarrhea? But she is a indoor/outdoor cat) and became super lethargic. She would go outside and never leave our porch. In addition when she came inside, she would go straight to the bedroom and sleep