Why Is My Cat Vomiting After Flea Treatment? 

If you’ve ever dealt with a flea infestation on your beloved feline, you know the struggle of trying to rid them of those pesky critters. But what happens when even after investing in products specifically designed for dealing with this problem, your cat ends up vomiting? Vomiting after flea treatment is unfortunately one of the common side effects cats can experience from topical treatments like spot-ons and shampoos if they ingest the product. It’s a frightening situation that no pet owner should experience, and it can be hard knowing how to approach the matter. Continue reading below to learn why it might be happening and what measures you can take if it does occur. 

Side Effects of Flea Medications 

Topical flea and tick medications have active ingredients and a carrier that help the product stay on your cat’s skin. If your cat licks the medication before it has dried, it can cause various symptoms such as hyperactivity, agitation, nausea, vomiting, foaming at the mouth, and excess salivation due to the bitter taste. To counteract this, you can give your cat fresh water and wet food or tuna to mask the taste. If you’re worried about the medication, you can give your cat a bath using liquid dish soap, such as Dawn, to remove it. 

If you have a dog that was treated with a permethrin product and your cat licks the area before it has dried, or you accidentally applied a dog flea medication to your cat, it’s crucial to be aware of the potential risks. Permethrin, an insecticide commonly found in dog flea and tick products, poses a high risk for cats due to their heightened sensitivity to this chemical. If you catch this quickly and do not see any symptoms yet, you can bathe them three consecutive times using liquid dish soap to get rid of the product. However, if your cat is seizing or tremoring, it is imperative to take them to a veterinary clinic immediately. 

Reactions to Flea Medications 

If your cat is having a reaction, such as vomiting, after being treated with a flea product, you should call your veterinarian and Pet Poison Helpline right away. Potential adverse effects to flea medications include: 

  • Profuse drooling 
  • Vomiting 
  • Tremors 
  • Hyperexcitability 
  • Agitation 
  • Seizures 
  • Weakness 
  • Difficulty breathing 


If your cat is having a bad reaction to a flea product that was applied, remove the product right away by bathing them with dish soap. Call your veterinarian and Pet Poison Helpline at (855) 764-7661 for help to determine what the next steps should be. If they were exposed to pyrethrins/pyrethroids and are left untreated, death can follow. Just to be safe, take your cat to the veterinary clinic so they can receive treatment. To avoid any poisoning mishaps, always consult your veterinarian before administering any medication to your pet. They can determine what is safe for your cat and give you directions on how to safely apply the product.