Advantage for Cats & Vomiting

Flea medication could have an unfortunate side effect on your cat.
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Few things ruin a happy snuggle with your kitty more quickly than seeing tiny fleas hopping about on Miss Sassy Pant's back. Advantage flea medication kills fleas through monthly applications, but the side effects may cause some concern for your kitty's health.

Advantage's Advantage

Completely ridding your cat of fleas takes more than just a few combings or baths with anti-flea shampoo. Every stage of the flea's life cycle must be addressed, from egg to adult. Advantage's active ingredients imidacloprid and moxidectin basically poison the adult flea, causing paralysis and ultimately death. Eggs laid before the poisoned adult dies are defective and either do not hatch or result in larvae unable to mature. This protection lasts for 30 days before re-application is required.

Side Effects

Common sense tells you that using something that essentially poisons a flea may cause some undesirable side effects to the cat. In most cases, side effects are fairly mild and include skin irritation at the application site and an oily residue coating the fur. Your cat may act a little jittery, which may only be related to the feeling of something wet on her back that she can't reach to clean away. These reactions fade after a day or two with no lasting effects.

Serious Symptoms

Sometimes the side effects your cat experiences aren't so common or mild. If your cat manages to lick the application site, she may drool like crazy to rid her mouth of the taste, or she might start vomiting. The chemicals in the medication work by absorption into your cat's oil glands, and some cats react badly to the medicine's presence in their bodies. Behavior changes could occur, including lethargy, restlessness or aggression, and she could develop diarrhea, appetite changes and increased thirst.


Serious reactions to a flea medication are not a fix-it-yourself type of medical condition. If your cat vomits after you apply Advantage, offer plenty of cool, fresh water to keep her hydrated, and call your vet. Make note how long it's been since the treatment application, how many times she has thrown up and what the vomit looks like. Gross, yes, but it could be helpful in narrowing down the culprit. Sometimes it could be a coincidence – she had a hairball that just had to come up at that particular moment – but if it occurs more than once and has you concerned, pick up the phone.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.

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