Adverse Reactions To Cat Flea Products

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Adverse reactions to topical veterinary-prescribed flea treatments are rare but can happen in some cats. Topical flea products (known as spot-on) have made the treatment of fleas, ticks and parasitic worms so much easier than tablets and pastes. These products are applied to the skin on your cat’s neck (between the shoulder blades) once a month, or as directed.

Common topical flea products include Frontline, Revolution, Program and Advantage.

Common symptoms

  • Foaming at the mouth – This usually occurs when your cat has licked some of the product which has a bitter taste and is self-limiting.
  • Hair and skin loss – Some particularly sensitive cats can receive chemical burns from topical flea products. Mild cases result in hair loss; more severe cases will also cause a loss of skin.
  • Contact dermatitis – A local reaction to the product. Symptoms can include tingling, itching and scratching, redness, rash and in more severe cases, blistering and ulceration.
  • Poisoning – Poisoning can occur if the cat is treated with a dog flea product. This may be deliberate or accidental if the cat comes into contact with a dog who has been recently treated and can cause severe tremors and seizures. Take care when treating a dog for fleas if you have a cat in the house, or better still, switch to an oral chew treatment. Common symptoms include drooling, ear twitching, ataxia (wobbly gait), muscle tremors, seizures.

Always seek immediate veterinary treatment for a poisoned cat.

How to help a cat who has a reaction

Chemical burns:

If your cat suffers a chemical burn to a flea product, rinse the area with lukewarm water for 20 minutes and take the cat to a veterinarian. If the cat resists having his or her fur rinsed, go straight to the veterinarian.

Licked off product:

Wet a washcloth and carefully wipe the inside of the mouth to remove any residue. Offer the cat a drink of water or some food.

Flea treatment poisoning (overdose or administration of a dog flea product):

If possible, apply a small amount of dishwashing detergent such as Dawn or Fairy Liquid (the type you use to wash dishes in the sink) directly to the back of the neck where the product is, apply warm water, lather and rinse the detergent off. Do this two to three times, wrap the cat in a towel to keep them warm and then take the cat to a veterinarian. Bring along the product packaging which will list the active ingredient.

Preventing a reaction

  • Always apply the product as directed.
  • Never use a dog flea treatment on a cat.
  • Always buy flea products from your veterinarian, be wary of over the counter flea products in supermarkets, most are ineffective, and some can be dangerous.
  • Don’t use multiple flea products at the same time (for example topical flea products in conjunction with a flea collar), unless advised to do so by a veterinarian.
  • Never apply a topical flea treatment to skin which is red or damaged.
  • Do not use flea products on kittens under the age of 8 weeks (12 weeks with some brands) unless the product is marked as safe for young kittens. Read the instructions to make sure your kitten is old enough to receive treatment.
  • Always check with your veterinarian before applying flea products to kittens OR their mother.
  • Seek veterinary advice before applying a flea product to an elderly, pregnant or sick cat.
  • If you have a dog and a cat, check to see which products are safest to use to help avoid toxicity.
  • Have one member of the household responsible for flea treatments to prevent an accidental double-up of treatment. Keep a note of the date the cat was treated. For monthlies, it can help if you nominate the first or the last day as treatment day, or at the start of each season for quarterly treatments.




Julia Wilson is a cat expert with over 20 years of experience writing about a wide range of cat topics, with a special interest in cat health, welfare and preventative care.Julia lives in Sydney with her family, four cats and two dogs. She enjoys photography, gardening and running in her spare time.Full author bio Contact Julia