17 surprising ingredients bad for Cats and reasons to be cautious

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What can cats not eat? Cats re obligated carnivores. They have evolved eating a diet of prey, which involves meat, bones, muscle and fat. As they evolved, they also started to change their diet. Now they are eating cat food we feed them, apart from the occasional mouse or bird they catch from time to time if they go outside!

This evolution from carnivores and hunters to your sweet, curious and playful kitty, have created a toll on their digestive systems, and sometimes your cat will eat something that his or her system will not process properly, which might damage your cat´s health on the long run.

No matter how much your furry friend gives you the irresistible eye´s look in order to beg for what you are eating. These are foods that cats can not eat. [1]


cat alcohol

We should never give anything containing alcohol to your cat, as this substance is very poisonous. But not only alcoholic drinks. Alcohol poisoning occurs when a cat ingests substances containing ethanol (like alcoholic drinks and liquid medications), isopropanol (such as flea sprays that are alcohol-based), and methanol (as in windshield washer antifreeze). Toxicity occurs rapidly as the alcohol is quickly absorbed into the cat´s system.

Cats that have consumed toxic amounts of alcohol will show symptoms shortly after the ingestion. These could be:

  • Vomiting
  • Disorientation
  • Inebriation
  • Loss of bodily control (ataxia)
  • Diarrhoea
  • The excitement which changes to depression
  • Difficulty breathing (dyspnea)
  • Loss of consciousness
  • Dehydration
  • Slow heart rate (bradycardia)
  • Seizures
  • Heart rhythm problems

If you suspect that your cat has ingested a product like rubbing alcohol, uncooked bread dough, or cough medicine, or if it is reacting to a shampoo, call your vet immediately. Symptoms can range from mild intoxication to severe.

Good news is that the majority of cats wouldn’t drink alcohol, as the flavour and smell work as a repellent for them, but beware holiday stress can cause your pets to act in ways they normally wouldn’t, like table surfing or digging in the trash for leftovers. So, avoid any dangerous situations for your pet by keeping any risky drinks out of their reach and making your guests aware of the dangers that alcohol, beer, wine and many foods pose for pets. [1] [2] [3]

Coffee ( and caffeine in general)

Believe it or not, some cats like coffee! My cat also gets crazy with the smell of a tea and wants desperately to leak the teaspoon. Mental note: don´t let him/her.

But not only the coffee is dangerous for cats. Caffeine is a no-no for all felines. This includes coffee, tea, stimulant medication, energy drinks (what is your cat doing near a Red Bull anyway?)

According to the Pet Poison Helpline, It only takes ingesting a small amount to have toxic effects”. [4]

The dose of the caffeine varies depending on the size and weight of your cat. Drinking a splash of coffee is unlikely to contain enough caffeine to irreparably harm your cat, although it might make them sick; however, if your cat were to eat coffee grounds, it could lead to serious caffeine poisoning. Too much caffeine can even be fatal for a cat. This is also true in dogs.  [5]

Common symptoms of the coffee ingestion can be:

  • Vomiting
  • Diarrhoea
  • Loss of muscle control
  • Tremors
  • Seizures
  • Collapse

The onset of caffeine poisoning is usually marked by severe hyperactivity. If you are aware that your cat has ingested caffeine in any form, take it to the vet.

Be aware that the coffee also contains Theobromine and Xylitol, which is also toxic to cats.

When you finish your morning brew, make sure the grains of coffee is out of reach from your pet’s paw. Also no matter how much your furry friend begs, do not let them finish your cold coffee. I know my cat would love to!


We all love chocolate in all shapes and forms, and it even has some good effects reported in humans, like serotonin, which an increase in this elevates our happiness. Unfortunately, it doesn’t work the same way for cats. Stimulants are a no go for cats.

Chocolate contains a chemical called Theobromine, which is poisonous to cats. Humans easily metabolize theobromine, but cats process is much slower, allowing it to build up to toxic levels in their system.

Also contains Xylitol, an artificial sweetener which is poisonous to cats.

The darker kinds of chocolate contain more quantity of theobromine.

No amount of chocolate is safe for your cat, but with large amounts, theobromine can produce the following symptoms:  [6]

  • Muscle tremors
  • Seizures
  • Irregular heartbeat
  • Internal bleeding
  • Heart attack. 

The onset of theobromine poisoning is usually marked by severe hyperactivity. Be aware that the smaller is the cat, the faster will get affected.

If your cat has eaten a box of chocolates, take it to the vet immediately. Do not wait to see if it gets better. Early treatment will help your cat recover quicker and lower your costs.

Never give a chocolate chip as a treat for a cat, as it can seriously damage your furry friend´s health.

Onion or Garlic

Normally your cat would avoid eating these ingredients naturally, but if your pet likes to eat everything he or she finds, make sure that it can’t get to these foods.

According to the Pet Poison Helpline, a 24/7 pet poison control centre, plants and vegetables in the onion family, such as garlic, leek, chives, contain Propyl Disulfide. This chemical destroys an animal’s red blood cells, causing anemia, wich in severe cases can do serious damage to the internal organs. [7]

The most commonly known symptoms are:

  • Nausea
  • Vomiting
  • Diarrhea
  • Lethargy
  • Abdominal pain
  • Increased heart rate

If you see any of these symptoms in your cat after eating Onion or garlic, please contact your vet.

Chewing gum and Candy

Most people would hide the chocolate, medication, teas, coffees, antifreeze from the reach of their furry friends  because of the bad effects of the Xylitol in their bodies. But has anybody thought on the chewing gum or the candy? If we take away the stickiness factor, it looks quite harmless, right? Well, not quite. Never give chewing gum or candy to your cat. [8]

Chewing gum and candy also have Xylitol, an artificial sweetener toxic to cats. A single piece of sugar free gum contains 0.3g of Xylitol. This means that a 4kg cat could start to have health problems after eating barely 3 pieces of gum. If this happens, your cat might have symptoms of hypoglycemia, which is a sudden drop of blood sugar. These could consist of:

  • Weakness
  • Lethargy
  • Collapse
  • Sometimes seizures.

If you suspect that your cat has eaten gum, please take him/her to the vet immediately, as will need to start treatment to avoid the absortion of Xylitol inmediately.


Some of us love cooking and making our own food. And who doesn’t love a good homely made from scratch oven-baked pizza? Even if we are not in Italy, it is still delicious. Bad news for our four-legged furry friend. The pizza dough is extremely dangerous for pets. 

Dough rapidly grows after ingestion, which can cause life threatening stomach distension and blockage. Also, the highest risk comes from the fermentation of the yeast in our cat´s stomach, which can lead into alcohol poisoning.[9]

A common scenario is when we prepare the dough and we leave it unattended over the counter all night so it rises, and we wake up to realise our beloved kitty has eaten it and is developing symptoms already. In that case it is really important to take your cat to the vet immediately, as will have to start treatment as soon as possible.

Ice cream (and any kind of cream)

Who hasn’t been on a warm day savouring a refreshing ice cream of your favourite flavour with your furry friend looking at you with those puppy eyes begging for an opportunity to savour that cone? Who hasn’t thought that it would be no harm in sharing a couple of licks with your pup?

Well, you are not really doing your cat a favour. Despite all the amount of sugar that goes with it, they will not enjoy it at all. 

This goes against every stereotype we have on cats, but the truth is, almost all the adult cats are lactose intolerant.

Symptoms that they will develop when eating ice cream will be

  • Diarrhoea
  • Vomiting
  • Gastrointestinal issues

And because of all the amount of sugar in it, they might end up having dental problems.

No matter how hot it is and how much do you think they will enjoy it, but don’t give any ice cream, or any kind of cream (including milk) to your dog or cat. 

Milk and derivates

Who hasn´t always seen a cute kitten drinking from a bowl of milk? Or even an adult cat? This is one of the most powerful stereotypes and associations there are regarding our fury friends. 

When we think about milk, we are thinking about cow milk, and not the milk from the kittens mother, which is the one to be fed naturally to a kitten until finishes the weaning process at 8-10 weeks. Kittens don´t need cows milk

In order to digest lactose, the digestive system must contain an enzyme called lactase. As mammals, we have plenty of it at birth, in order to be fed with our mother´s milk.

As we grow older the cat´s and human´s body produce less lactase, which means less ability to digest lactose. This will eventually lead into lactose intolerance.

The truth is, the vast majority of cats are lactose intolerant. When a lactose intolerant cat drinks milk, the indigested lactose passess through the internal tract drawing water with it. The bacteria in the colon, also ferment the indigested lactose, forming volatile fatty-acids. All that leads to an upset tummy. The most common symptoms are:

  • Diaehrroa 
  • Vomiting

If this happens to your cat, bear in mind a visit to the vet for further recommendations

Sometimes, a cat that is intolerant to lactose when drinking milk, seems to tolerate better other derivates, such as milk or cheese. This is because different milk derivates might have different quantities of lactose. This doesn´t mean you can give indiscriminate amounts of cheese to your cat. It might still trigger bad tummy on her. [10]

Grapes and raisins

Recently researchers and veterinarians have found that grapes, raisins and currants can cause kidney failure in cats. Poison ocurres on cats after the ingestion of seeded or seedless variants of grapes, commercial or homegrown, red or green types, organic or non organic fruit, and grape pressings from wineries. Also foods containing grapes, raisins and currants (such as raisin bran cereal, granola mix, trail mix or bake goods) are all potential sources of poison.

Unfortunately there is not a well established toxic dose for these. It is known that dogs become more poisonous after ingesting large doses of fruit. Also there is significant sensitivity amongst different dogs. This also happens in cats. Some kitties demonstrate more tolerance to the ingestion and others become poisoned after ingesting just a few grapes or raisins.

Symptoms of grapes, raisin and currant poisoning are:

  • Vomiting, which is generally seen within 24 hours following ingestion. 
  • Lack of appetite
  • Lethargy
  • Possibly diarrhoea can be also seen within the next 12-24 hours. 

More severe signs are not seen for 24-48 hours after ingestion – often after acute kidney failure has already begun.

If you suspect that your cat has eaten grapes, raisins or currants, please call the vet immediately. Don’t wait. [11]


Salt is bad for cats if they eat too much of it. For example, rock salt left unattended over the kitchen counter or foods with too much salt on them. If they eat too much salt, they will have to counteract it by making several trips to the water station. This applies to any of the spices.

Cats, as well as humans, need the sodium as part of the electrolyte balance, so small amounts are not entirely bad for your cat. Like most living things, cats need salt to help balance fluids and keep nerves functioning properly. Most cat food you purchase has sodium in it, either naturally occurring from ingredients in the food, or through added salt. So, salt, in moderation, is not bad for your kitty. In excess, however, it can lead to serious health complications and even death.

Too much salt can cause problems of 

  • Vomiting
  • Diarrhea
  • Lethargy
  • Swelling or fluid accumulation
  • Excessive thirst and urination
  • Tremors & seizures

Salt poisoning (hypernatremia) is life threatening. If your cat consumes a good quantity of it, please contact your vet for assistance. [12]


Nutmeg -and spices in general- is considered to be a moderate risk for your cat in terms of toxicity, and your kitty would have to eat big amounts of eat to have an impact on his health. However, this might be different depending on your cat´s age and health issues. 

Nutmeg contains myristicin, which is mainly found in the oil of the seed. It is toxic in cats and dogs when they eat around 5 grams of the spice. 

Signs of poisoning include:

  • Decrease in body temperature
  • Dehydration
  • Vomiting
  • Decreased production of saliva
  • Increased heart rate
  • Muscle tremors
  • Disorientation
  • Seizures, and even death

Symptoms can be seen as soon as 3-6 hours after the ingestion of the spice. It is important that if you suspect that your cat has eaten some amount of the spice you contact your vet immediately. [13]


Avocados have huge benefits for our health, so you should definitely incorporate them to your diet. But although they are very good for humans, we cannot say the same for cats. They contain a fungicidal toxin called persin

According to the Pet Poison Helpline, persin is a mild poison for cats and dogs, which if ingested by your pet in large amounts can provoke the following symptoms:

  • Gastrointestinal problems
  • Trouble breathing
  • Heart issues

It will not kill your cat if ingested, and definitely will have to eat a good amount of the flesh of the avocado for it to be toxic, but certain medical conditions would be worsened by avocados, so definitely avoid them if you can. You can substitute them by other foods that provide similar health benefits, but without the persin.

Also, the skin and the pits should never be offered to your kitty.


This could sound like another broken stereotype. Cats love tuna, that´s a fact, so how can it be bad for them? For sure Lucy-Lu, my beloved kitty absolutely loves tuna. All the tricks she plays to be able even to get a bite to eat deserves a medal. Of course if never ends with a bite… Who is going to tell Lu that she no longer can savour one of her favourite foods?

Well, good news for the tuna lovers, as per with every pleasure in life, moderation is key. Tuna is one of this foods that is good to have in small quantities, as it also have a lot of nutrients and benefits. 

A steady diet of tuna prepared for humans -canned or fresh- could lead into an unbalance, as your cat wouldn´t be getting all the nutrients he or she need. Also, too much tuna can lead into mercury poisoning, which symptoms include:

  • Dizziness
  • Loss of coordination and balance

Never give tuna to your cat as a main ingredient of his or her diet. Always treat it as an occasional treat

If your cat develop any of the above symptoms after eating fish, contact your vet.

Raw fish

Cats are fish lovers, and wherever there is a fishmonger, there will be cats waiting for their delicious price. At least that is part of our collective imaginary, right? 

Well, this is another of those foods where moderation is key. Consuming it in small quantities is probably ok, but in consistent amounts or in large ones it could trigger health issues due to mercury found in larger quantities, especially in bigger fishes.

Also, Like with raw eggs, raw meat and fish can have bacteria that potentially could trigger food poisoning. In addition, some fish like salmon, trout, sturgeon, or shad, could transmit a parasite that can cause “fish disease” or “salmon poisoning disease”. [14]

If your cat gets any symptoms from eating raw fish, they would look like:

  • Vomiting
  • Fever
  • Big lymph nodes

If your pet gets any of these symptoms after eating raw fish or meat, take him to the vet immediately. 

Sugary Foods and Drinks

Cats don´t have sweet taste buds on their tongues. but the truth is they like it how we like it when it comes to sweets. They also can suffer from addiction to sugar, just like us. 

This explains how the brain works. When we eat or drink sugar, the nucleus accumbens area of the brain releases dopamine, which makes us feel good with ourselves. When sugar is consumed often and in increasing amounts, we reach some tolerance, which means that we need more sugar in order to produce the same quantity of dopamine. That’s how addiction to sugar is explained in both, humans and dogs. Also in cats too. The only different is that the cat is the only mammal we know that cannot taste it.

Unfortunately, like humans, cats suffer the same negative effects after regular sugar consumption:

  • Diabetes
  • Obesity
  • Dental problems, etc

You need to be aware of the ingredients list of some food brands when it comes to sugar, as some of them will add more in order to create addiction to that brand. Sugar also comes in many names and forms. 

Some of the most used in cat  food are: sucrose, caramel and corn syrup. Sorbitol is a sugar alcohol derived from fruits and berries, but it can also be created synthetically. Beet pulp is the by-product of sugar production from sugar beets. Fructose is very sweet and is derived from fruits.

Although honey and molasses have often been said to have medicinal properties, keep in mind they are both still sugars.

Small amounts of naturally occurring sugars, such as those found in the foods that make up your cat´s foods, are not bad. However, added sugars, especially those added to dog foods and treats, are not good for your cat. They can create an addiction and lead to health and dental problems.

Also high compsumtion of sugar in cats can lead into diabetes. [15]


Bones present a health hazard for your cat. 

Chewing is a natural cat behaviour, and bones are even full of minerals that are good for your pet, but you need to be aware of the fact that cooked chicken or even fish bones are bad and even dangerous for cats, as they break and splinter into small, sharp pieces that can cut your dog’s mouth or digestive system. 

Broken pieces of bones can cause: 

  • Mouth and tongue lacerations
  • Choking
  • Broken teeth
  • Cuts and wounds in the mouth or on the tonsils
  • Vomiting and diarrhea
  • Severe constipation
  • An intestinal blockage that may require surgery

The safest bet is never to give your furry friend anything on a cooked bone. Even the beef bones can break, causing the above symptoms. In addition to being unsafe, cooked bones are not as healthy as other bones, as the most part of the minerals and positive properties are stripped off in the boiling process.

Macadamia nuts

Who doesn’t like macadamia nuts? They are tasty, creamy, healthy, and a great source of protein. Also, they make a great ingredient when baking cookies, especially during the fall.

Although macadamia nuts are healthy for humans, it is not such a good idea for your pet. Your furry friend would only need to eat a small amount in order to experiment bad effects.

The symptoms in cats after eating macadamia nuts can be:

  • Diarrhea
  • Vomiting
  • Weakness in the back legs

In most cases these negative effects can be mild, and manageable at home, but in more serious cases, it has to be managed by a professional. Anyway, if you suspect your kitty has eaten macadamia nuts you should contact your vet immediately.

Symptoms for a stronger negative reaction might include:

  • Shaking constantly
  • High fever 
  • Unable to walk

If you see your cat vomiting experiencing lack of appetite, stomach pain or a decrease in activity level within three days of eating macadamia nuts, you should contact your vet immediately.

What can cats not eat? What´s next?

The bottom line is that there are foods that are an absolute no-no for your cat, as per their high levels of toxicity for them. Also there are another foods which it´s ok if they eat a little bit and in moderation

With cats being obligated carnivores they will eat what they suppose to eat, but what they are not suppose to eat might take them down the road with health problems, or even kill them.

Also, check what human foods are safe to give to your furry friend for more peace of mind.

In addition, why don´t you check our nutrition advice guidelines?

Dace Lace

Dace Lace

My name is Dace Lace. My love for my pets led me on a journey. Online forums and discussions opened more questions than answers. Also, I realized that there are more cat and dog owners out there looking for answers on the internet. However, some articles published was not backed up with science and I was uneasy about that.

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