Flea in cat or dog is the most headache problem for owners. It is blooding-sucking and parasitic. Not only make your cat feel bothersome, itchy, or suffer from a number of related illnesses, but fleas also threaten your house’s safety. Because after appearing on the cat’s body, its scratching itch or action causes the flea/ flea eggs to fall to the floor. And then, they will live and reproduce in and around your house. That is synonymous with members of your family who can have bloodsucking and infection with flea-borne pathogens. So getting rid of fleas for your cat is extremely important. At that time, your cat needs to be treated with flea medicine. But don’t forget the possible side effects of flea medicine for cats!


Fleas are small, wingless bloodsucking insects ( belong to Siphonaptera suite) with dance jumping characteristics. It mainly sucks animal blood. Base on the research, there are so many kinds of them. Most notably are mouse fleas, human fleas, and cat fleas. Cat flea (the scientific name is Ctenocephalides felis) is one of the most widely distributed flea species and has the largest population on the planet. And cat flea is a tapeworm transmission vector. In this article, cat fleas are the subject of this discussion. Because the main host for cat fleas is domestic cats (but this flea also infects most dogs in the world).

Cat is different from dogs. Cats can get very sick (or even die) if they are treated with flea medicine for dogs.  Therefore, make sure that the medicine you choose is for cats, not dogs (there are many cat flea products whose names are identical to those used for dogs).

Side Effects Of Flea Medicine For Cats
Credit : wikihow

Signs of flea bites

Fleas can hide anywhere on the cat’s body. Always pay attention to your cat to promptly detect if it has fleas or not. Flea bites are very itchy, and the surrounding skin can be sore or throbbing.

Some signs:

  • Cats excessive grooming of the fur: That happens when your cat is sensitive to fleas, it will have an allergic reaction or itching caused by a flea bite.
  • Cat skin is irritated, especially in the back of the neck and the base of the tail.
  • There are small lumps or scabs, usually on the neck and spine.
  • Behavior away from familiar places.
  • Act restless, irritable, or act like a growl and shake its head. Perhaps your cat is trying to shake off the flea.
  • There are tapeworms in cat droppings.
  • Cats are listless and tired of anemia…

When your cat is bitten, itchiness makes it a scratch. Excessive scratching can further damage the skin and secondary bacterial infection. Fleas can cause anemia, especially in kittens, the simultaneous transmission of other diseases, including Rickettsia and Bartonella fever. Therefore, your cat needs to be protected by flea medicine.


Flea medicine for cats

You need to choose the right medicine for the cat and follow the veterinarians’ instructions because some of them sold at the pet store can be dangerous for cats.

There are two kinds of flea medicine for cats: topical medicine and oral medicine.

Topical medicine

You will have more options when looking for topical medication for flea bites for cats. In addition to monthly recurring treatment, you should give it to your cat yearly as a precaution. This medicine is applied directly to the cat’s skin for a faster effect.

Moreover, make sure that you use topical medicine properly for your cat. Note that the bottle must be kept upright so that the liquid does not spill and must be opened according to the instructions. Strip the fur on the cat’s neck (just below the skull or between the shoulder blades) to reveal the skin and then apply the medication to the area. By the same, your cat will not lick the medicine when brushing. Or you could apply the medicine to any areas where your cat is attacked by fleas. Make sure that medications are absorbed into the skin, not just on the fur. Besides, always read the product label carefully to know how to use it correctly, because each medicine may have different uses.

Some Topical medicine

   •  Dinotefuran and pyriproxyfen ( known with the name Vectra): This medication just only kills fleas. Note that you do not choose the wrong product with the same name, Vectra 3D, a product for dogs. Note that it contains permethrin which is harmful to cats, even fatal. Give your cat this medication as directed by your animal doctor.

   •  Fipronil and (S)-methoprene  (known with the name Frontline Plus for Cats): This medicine kills larvae, eggs, and adult cheta bugs.

   •  Imidacloprid and pyriproxyfen (known with the name Advantage II): This Topical medicine kills fleas at every stage of their life cycle. Make sure that you do not choose the wrong product with the same name, Advantix II, which is a product for dogs. Just like Dinotefuran and pyriproxyfen, Advantage II contains permethrin. You need attention!

   •  Selamectin (known with the name Revolution): Apply this medicine every month to kill adult fleas and its eggs.

Oral medicine

This is the solution for your cat if it only needs to kill fleas, not ticks. Oral medications may come in suspension or tablet form.  The advantage of oral products is that they work quickly and do not leave excess medicine on the cat’s fur. This medicine is only prescribed by an animal doctor. And you can consider using the drug-treated monthly as a preventive measure by taking it year-round.

Some Oral medicine:

• Lufenuron (known with the name Program): This medicine comes in tablet, suspension, and injection form. It kills flea eggs and larvae. Give it to your cat with food once a month.

• Nitenpyram (known with the name Capstar): This medicine takes the form of a pill and works to kill adult fleas and its eggs. With this oral medicine, you need to follow the vet’s instructions so that your cat is given this medication properly.

   • Spinosad (known with the name Comfortis): Spinosad comes in the form of chewable tablets. So you should use it to your cat together its food once a month to kill the flea.

Side effects of flea medicine for cats

Side effects of flea medicine can cause some symptoms:

Redness and itching

Cats may have redness and itching in the skin areas where the medication is used. When your cat meets this case, the best way is to wash the area with redness to completely remove the medication on the cat’s skin.


It can be said that epilation is the most common side effect in cats when using flea medicine. However, you should not ignore that. Consult your veterinarian to find a better flea treatment and less fur loss in pets. This is considered a mild case and does not affect your cat’s health.

A bit around the base of the tail

When the cat is treated by flea medicine but not effective, fleas will reappear in your cat. The first place is the tail. According to Dr. – Veterinary dermatologist Milivoj Milosevic, many products are known to work within 30 days. Still, in fact, the medicine will start to work less effectively from the third week. In that case, you need to consult your veterinarian to choose a new drug. There are some medications that work long ( 3 or 8 months) for you to choose from.

Vomiting and diarrhea

These are manifestations of the side effects of flea medicine in pill form for cats. In addition to that, this situation may also occur when your cat licks the medicine, which is applied to the skin. When cats lick in large numbers, the risk of mouth ulcers is very high. So you need to pay more attention to your pet. An effective method, in this case, is to wear an anti-lick cat collar.

Muscle twitching

Some of the common ingredients in cat flea medicine like Permethrin, Cyphenothrin that cause side effects in cats can lead to death. Before using flea medicine for cats, let bring cats to the veterinary station to be sure of the cat’s condition and choose flea killer products suitably. If your cat shows signs of muscle twitching, immediately take it to the nearest veterinary station for inspection and treatment.

Final thoughts

Just like humans, cats need to be prevented and cured in a timely manner. It is not arbitrary for cats to use the medicine, to thoroughly understand the situation that cats encounter and to get advice from veterinarians to treat. 

Besides, do not forget to consider the side effects of flea medicine for cats, particularly any medications you use for cats in general.


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