What To Do if Cat Acting Weird After Flea Treatment

Fleas are the leading cause of skin and parasitic infections in cats. Because cats are very curious animals, they can pick up fleas rather easily. As a matter of fact, up to 18% to 19% of cats have fleas. The good news is that a flea infestation is highly treatable. However, once upon a time, you may have noticed a cat acting weird after flea treatment.

There are five most common reasons why the cat may act weird after flea treatment. An unfavorable reaction leads the list, which can be due to the cat’s sensitivity to the ingredients or accidental ingestion of the product. In some instances, a cat may act weird after flea treatment as a result of stress and anxiety.

Dealing with a flea infestation in cats can be done in many ways. Two of the most popular include applying a spot-on flea treatment and using an anti-flea collar. Some cat owners prefer taking a trip to the vet.

Regardless of which flea treatment you prefer, it’s possible for your cat to act weird afterward. Sometimes, it’s completely normal for a cat to exhibit unusual behaviors after having its fleas dealt with. However, in most instances, it could be due to your purring pal’s unfavorable reaction to the anti-flea treatment’s active ingredients.

Keep on reading to know some of the potential reasons behind a cat acting weird after flea treatment.

Now that you know some of the things that could happen if your furry pet has fleas and the most popular flea treatments, too, it’s time to check out some of the reasons why your cat may act strangely after flea treatment…

Five Reasons of Cat’s Behavior After Flea Treatment

cat flea treatment
Image credit: Canva

Cat’s Sensitivity to the Flea Treatment Ingredients

The majority of flea treatments have to be toxic to fleas to work. While many of their chemicals are safe for felines, some cats may be more sensitive to them than others. If your cat develops a bad reaction to one or many ingredients of the flea treatment of your choice, it’s not unlikely for it to act weird.

Just because a particular flea treatment has worked effectively for your neighbor’s cat doesn’t necessarily mean that it will work very well for your cat without any trouble.

This is when the sheer importance of consulting a vet when dealing with fleas comes in.

In some instances, cats that are extremely sensitive to the ingredients of flea treatment may wind up having flea treatment poisoning. Some of the signs and symptoms include:

  • Drooling
  • Vomiting
  • Lethargy
  • Diarrhea
  • Uncoordinated movement
  • Muscle tremors
  • Seizures

If you notice any or more of the above, take your cat to the clinic and bring the flea treatment’s packaging, too.

Many anti-flea collars for cats contain all-natural ingredients only. Some of the most common ones include cinnamon, peppermint and geranium.

Even if an anti-flea collar relies on nothing but substances obtained from nature, your cat may still exhibit signs that it’s sensitive to its ingredients. For instance, the product may irritate its nose or skin.

In fact, the first time that you remove an all-natural anti-flea collar from its packaging, you may notice that it has a very strong smell. You may also have a difficult time putting it around the neck of your writhing cat.

Accidental Ingestion of the Chemical

Do you have several cats, and all of them have just been treated for a flea infestation?

Then it’s very much possible for them to ingest the chemicals in the flea treatment employed by accident — they can consume them when they groom or play with each other immediately after getting the treatment.

Because of this, cats should be isolated for at least two hours after the application of the product. This is to give the anti-flea treatment plenty of time to get absorbed by the skin.

It’s a different story if the treatment of choice is an anti-flea collar.

What’s so nice about an anti-flea collar is that it can provide results for five to eight long months.

On the other hand, a spot-on flea treatment’s effect can last for only about one month.

But for an anti-flea collar to keep your cat free of fleas for months, it should be worn by your pet all the time.

The problem with this is that your cat can ingest some of its chemicals when it attempts to remove the collar with its hind leg and then licks it. Similarly, if you have multiple cats and all of them are wearing anti-flea collars, some sort of cross-contamination can take place without trouble and cause them to act weird at the same time.

If you have several cats and putting their health and wellbeing in danger is not an option, ask your trusted vet about the safest way to get rid of their fleas.

Using Incorrect Type of Flea Treatment

Fleas that can infest cats and dogs are different species. Despite this, each of them can infest the other — cat fleas can live on dogs and drink their blood, and dog fleas can live on cats and drink their blood.

Anti-flea collars are available for both cats and dogs. However, it’s a terrible idea to use an anti-flea collar designed for dogs on your cat. That’s because an anti-flea collar for a dog may contain permethrin, a synthetic insecticide. The problem with permethrin is that it’s toxic to felines, but canines tolerate it very well.

It can take a very long time for a cat’s body to break down permethrin, which is why it can cause toxicity.

This is why if your cat is acting weird after an anti-flea collar is placed around its neck, check that the product is intended for cats and not for dogs.

And while you’re at it, take a look at the list of ingredients — if permethrin is mentioned, remove the anti-flea collar right away. Some anti-flea collars for cats contain small doses of permethrin.

In some instances, it’s not the ingredients of the anti-flea collar that could make cats behave in a peculiar way after getting a flea treatment. Sometimes, it’s the collar itself.

Here’s a quick experiment…

Remove the anti-flea collar and replace it with an ordinary collar. If your cat acts in the same strange manner as it did when it was wearing the anti-flea collar, then it could only mean that your cat does not like wearing a collar. Put the anti-flea collar back on and distract your kitty cat for a while until it forgets about wearing it around its neck.

Treatment-Induced Stress and Anxiety

No one loves going to the dentist to get a root canal. Similarly, no cat loves going to the veterinarian to get its bum poked with a thermometer and its skin jabbed by a needle.

Because it can be extremely stressful and nerve-racking for a feline to be taken to the clinic, let alone see its owner take its carrier out of storage, it’s very much possible for it to behave unusually before, during and even after taking it out of its comfort zone and getting a flea treatment at the veterinarian’s office.

Some telltale signs that your cat is anxious and stressed include:

  • Increased vocalization
  • Dilated pupils
  • Breathing with the mouth open
  • Drooling
  • Rapid heart rate
  • Tightly curled position
  • Hair standing on end
  • Aggression

After getting its flea treatment at the vet, it may continue to act weird for the next few hours or days. Some of the things that you may notice include hiding, loss of appetite, lethargy and failure to use the litter box properly.

For most cats, a trip to the vet can be an overwhelming experience. If your meowing buddy is one of them, it’s a good idea to take it to the vet only when really needed to save it from unnecessary stress and anxiety.

Needless to say, consider opting for an anti-flea collar or spot-on flea treatment approved by your trusted vet than taking your cat to the clinic.

However, do take note that even a flea treatment carried out at home, such as putting an anti-flea collar around its neck or applying a spot-on flea treatment on its back, may still leave your cat a little shaken.

Sensation Caused by Agitated Fleas

Image credit: Canva

When quick-acting anti-flea treatments are used, such as those that are applied between the shoulder blades or injected into the fatty layer under the skin, fleas can die in as short as 24 hours only.

However, it doesn’t necessarily mean that fleas will die instantly the moment they ingest the chemicals in fast-acting anti-flea medications.

Before they drop dead, fleas become agitated, which could be sensed by the cats they’re living on.

There is something that veterinarians call the tickle effect.

Put simply, it’s the tickly sensation that felines feel as dying fleas move around in hope of finding a place where they’re safe and protected. When cats sense the overly active fleas on their bodies, they may run around, scratch, rub themselves against surfaces, vocalize, and pant.

Worry not because your cat’s strange behavior after getting flea treatment will go away on its own, usually when all the fleas on it are already dead and no longer moving around.

In some instances, it’s not the tickle effect that is making cats behave in a weird fashion but an unfavorable reaction to the active ingredients in the anti-flea solution used.

For instance, some chemicals may cause a pins and needles sensation in some cats sensitive to them.

This can cause felines to try all sorts of things to attain relief from the unusual sensation. Some of them include scratching their paws or tails with their teeth and rubbing themselves along the floor, wall or furniture.

Most of the time, the pins and needles sensation resolves on its own after a while.

Why And How to Treat Cat From Fleas

Refrain from assuming that your cat won’t get fleas because you keep it indoors.

Your cat doesn’t have to step foot outside your home just to get fleas. In many instances, fleas can step foot inside your home and infest your cat!

You, your family and friends, other animals, potted plants, secondhand items — all of these can introduce fleas to your cat.

As soon as you notice the presence of fleas on your purring pal, it’s a good idea to spring into action right away and deal with the infestation before serious problems come into being.

Some of the many complications of failure to keep fleas on your cat in check are:

Prevent Open Sores

Your cat may scratch aggressively not only when fleas bite but also each time they crawl from one point on your pet’s body to the other.

And because your feline friend has sharp claws, it’s not unlikely for open sores to come into being as a result. Those open sores can become infected if bacteria act upon them.

Stop Hair Loss

Besides open sores and secondary infections, excessive scratching due to a flea infestation can also cause hair loss. Bald spots can easily mar the appearance of your cat. The good news is that its hair will grow back once the fleas are eliminated. The sooner the problem is resolved, the quicker your cat will look healthy and adorable once again.

Avoid Flea Allergy Dermatitis

Sometimes, a cat may experience severe itchiness and scratch violently because of flea allergy dermatitis.

As the name suggests, it’s a form of dermatitis resulting from flea bites, and it can cause skin infections, scabbing, and hair loss. If your cat has this skin condition, it only means that it’s allergic to the saliva of fleas.

Avert Possibility of Cat Anemia

Many things can cause a cat to suffer from anemia.

One of them is a severe flea infestation.

Fleas can drink lots of blood, which can deprive a cat’s vital organs of much-needed oxygen — the blood, the red blood cells (RBCs), in particular, are the carriers of oxygen. Kittens and small adult cats could die due to severe anemia caused by fleas.

Treat Parasitic worms

Some fleas that live on cats carry tapeworm eggs.

If your cat has them, it’s likely to end up ingesting them by accident each time it grooms itself. This can cause the tapeworm eggs to hatch in your cat’s intestines, causing an infection.

In cats, tapeworms can cause weight loss. By the way, you can get tapeworms from your cat!

Avoid Getting Scratch Disease from Cat

It’s not just a tapeworm infection that you can get from your four-legged friend but cat scratch disease, too.

This can give you fever, headaches, loss of appetite, fatigue, and swollen lymph nodes. It can make your pet experience these things, too. Cat scratch disease is due to Bartonella henselae, a bacterium that fleas can transmit to felines.

Fortunately, there is no need for your cat to end up having one or more of these problems. It’s because there are many flea treatments available for felines that are effective and safe — well, some have side effects.

Let’s take a quick look at three of the most well-known among cat owners:

Use Anti-flea Collars

Many cat owners prefer to deal with fleas with the help of anti-flea collars, and it’s for different reasons.

Leading the list is the fact that they are cheaper than other available solutions. Anti-flea collars can be as cheap as $6 only. Also, these products can be easily bought online and offline without a veterinarian’s prescription.

The majority of anti-flea collars look nice, too, which can make cats look their best while being rid of fleas. However, some anti-flea cat collars contain irritating or toxic ingredients to which some felines may react unfavorably.

Try Spot-on flea treatment

Despite being more expensive than an anti-flea collar, many cat owners prefer to go for a spot-on flea treatment.

That’s because it tends to yield results quicker, sometimes in as short as 24 hours only. It also kills fleas no matter where they are on the cat’s body. Some spot-on flea treatments are prescription, while others are OTC.

For best results, a spot-on flea treatment, preferably one that your trusted vet recommends, should be applied to your cat every four weeks, which can cause the cost of dealing with fleas to pile up rather quickly.

Consider Injectable Medication

Then there is also an injectable medication that can get rid of fleas on your cat. Needless to say, it requires a trip to the nearest veterinary clinic for the drug’s proper administration.

Different injectable flea treatments are available. Many of them can help deal with fleas for a long time.

For instance, one option can help keep your feline friend free of fleas for the next six months. But since the drug is pesticide and injected into your cat’s body, serious side effects such as tremors and seizures are possible.


It’s of utmost importance to put a flea infestation to an end. Otherwise, your cat could end up with hair loss, open sores and secondary skin infections. It could also wind up with parasitic worms if it accidentally ingests infected fleas or anemia if the fleas consume large amounts of its blood.

The good news is that there are many ways to deal with fleas in cats. Many cat owners prefer spot-on flea treatments and anti-flea collars because of their accessibility and trouble-free administration.

However, a cat acting weird after flea treatment is a possibility. It can be due to many reasons, and one of them is the cat’s extreme sensitivity to the ingredients. If you notice weakness, falling over, excessive salivation, vomiting, diarrhea and tremors in your cat after treating its fleas, take it to the vet ASAP.

Similar Posts