Flea Medicine Side Effects on Cats

As a pet owner, it’s your responsibility to keep your furry family members healthy, and that includes administering the appropriate medication safely when needed. One of the most effective ways to treat and prevent fleas and ticks is through the use of flea medications. When dealing with fleas, it’s normal to worry about the side effects flea medications can have on cats. Continue reading to learn about the potential effects flea medications can have so you can make an informed decision when it comes to treating your furry friend.  

Potential Side Effects of Flea Medications

Topical flea and tick medications contain active ingredients and a carrier that adheres to your cat’s skin. Be sure to let the medication dry entirely so your cat can’t lick off the product. Otherwise, if ingested, the medicine may cause agitation, hyperactivity, vomiting, foaming at the mouth, and excessive salivation due to the bitter taste. If your cat ingested the medicine, you should give them fresh water and wet food or tuna to mask the unpleasant taste. If you want to remove the product from their skin, give them a bath with liquid dish soap. 

If you have applied a Permethrin flea product on your dog or accidentally used it on your cat, there are risks to be aware of. Permethrin is an insecticide that repels or kills fleas and ticks, commonly found in dog flea products. Unfortunately, cats are highly sensitive to this product, and exposure can lead to severe health complications. If your cat is not showing symptoms after exposure, bathe them thoroughly three times with liquid dish soap to remove the product from them. If your cat is exhibiting symptoms such as tremors or seizures, immediately take them to the veterinary clinic for medical help.  

Signs of Poisoning 

If you’ve applied a dog flea product to your cat or they have ingested a flea product they may experience negative side effects. Potential signs of poisoning include: 

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


If your cat is having an adverse reaction to a flea product you’ve applied or they accidentally ingested, you have to remove the product from their skin by bathing them in dish soap. Call your veterinarian and Pet Poison Helpline at (855) 764-7661 for first aid advice. If you cat has been exposed to pyrethrins/pyrethroids found in dog flea products and they are not treated, death can occur. You must always consult your veterinarian before administering any treatment to your pet so you can avoid any potential disasters. Your veterinarian can determine what medication will be best for your cat and will give your specific instructions for application. If you have any further questions or concerns about flea treatments for pets, don’t hesitate to call Pet Poison Helpline.