written by Rafael Rybandt

Food allergy and intolerance in cats


Does your cat suffer from recurrent diarrhoea, stomach pains and itching? In addition to mites, pollen and house dust, food intolerances are a commonly overlooked cause. If your cat cannot process its food properly, digestive complaints will be an everyday occurrence. But you can help your cat! With a couple of helpful tips and tricks, you can restore your cat’s vitality – in spite of food allergies or intolerances. We explain what you need to know about intolerances.

 If you suspect your cat is having problems digesting its food, you should book a visit to your vet. They will be able to tell you if the issue is a food allergy, an intolerance or another illness.



A food intolerance is a metabolic disorder which results in the substances being supplied not being processed properly.

This disruption to the normal digestive process can be caused by an enzyme deficiency. If enzymes are lacking that are essential for digestion, the cat may be unable to digest one or more components in its food.

By the way: contrary to popular belief, adult cats are often no longer able to properly process lactose (the sugar component of milk), even though they were able to do this as kittens.

The reason for this is that lactase production in the body gradually diminishes as the cat grows until eventually it is lactose intolerant.

In contrast to a food intolerance, a food allergy involves the body’s immune system – to be more precise, a defensive immune response is triggered.

This means your cat’s immune system treats the substance causing the allergy like a pathogen and responds accordingly. 

Typical symptoms include diarrhoea, itching, ear infection or even allergic shock.

The following symptoms could indicate a food intolerance of your cat. In case of any doubt, you should not hesitate to contact your vet. The cat may experience one or more of the following symptoms:

  1. Vomiting, which occurs only after certain types of food
  2. Flatulence after certain types of food
  3. Stomach ache
  4. Itching, often particularly on the face, ears and paws
  5. Flaky skin
  6. Unusually severe hair loss
  7. Inflamed or reddened patches of skin
  8. Poor appetite and weight loss
  9. Growth abnormalities
  10. Lethargy, apathy
  11. Coughing, sneezing and sniffles
  12. Reddened, inflamed eyes

There can be various causes of food intolerances in cats. For example, an allergy may develop due to a genetic predisposition, pollutants, or a change in lifestyle. But it is also possible for a food that your cat has eaten and tolerated well for years to suddenly trigger an intolerance. Unfortunately, food intolerances and allergies often remain undetected for a long time because cat owners sometimes fail to notice the symptoms, or their cat likes to roam outdoors and only exhibits symptoms when out, or perhaps the symptoms are attributed to another illness.

1. Age-related conditions

Some cats develop a food intolerance as they get older. Owners are often amazed to find their cat can no longer tolerate a food they previously consumed with no issues. Possible reasons for this could be an age-related complaint – or a food intolerance resulting from a change to the enzyme activity in the digestive tract. In simpler terms, certain ingredients can no longer be digested properly. A single exposure to the trigger substance is enough for the cat’s body to react negatively to it.


2. Changing food too often


Cats often fail to cope well with frequent switches of food, e.g. between wet and dry food, or regularly trying out new types of food.

They develop food intolerances, with symptoms that can include diarrhoea. If you frequently change food brands, you are taking the risk that your cat may not respond well to a particular manufacturer. We recommend avoiding changing cat food manufacturer too often once you have found a product that suits your cat.
Doesn’t that get monotonous as time goes by?

Not with us! At Green Petfood, our wet and dry food varieties are carefully coordinated, so you can spoil your cat with different flavours, and it will never get bored.

No danger of nutrient deficiencies: our blend of ingredients is specially designed to supply your cat with all essential nutrients, while also offering an appetising and varied menu.


Our simple blend is designed to ensure plenty of variety in your cat’s bowl. To meet the daily energy requirements for a cat with an average weight of 4 kg, you can use the following rule of thumb: 40 g FairCat Safe dry food plus 1 pouch of your choice from the FairCat wet food range! Absolutely scrumptious and a guaranteed happy cat!

3. Artificial additives in cat food

Artificial flavours and other additives, such as colourings, flavour enhancers and stabilisers, are often used in cat food production to ensure a consistent product quality. These additives can cause intolerances in cats.

4. The most common triggers: “incorrect” sources of protein

Most food allergies continue to be caused because cats react to specific proteins in types of meat or cereal contained in their food. The following are the chief culprits when it comes to food allergies or intolerances:

  • beef
  • dairy products
  • eggs
  • cereals or soya products

Product tip

Our FairCat Sensitive is ideal here because it has just a single source of protein: animal welfare chicken. Like all our other wet food varieties with grain-free recipes, it is particularly good for cats with food allergies. In addition, our FairCat Beauty and FairCat Fit include salmon from a more species-appropriate husbandry to protect your cat’s digestive tract. The gluten-free recipe plus chicken and insects in FairCat Safe are kind to the environment as well as your cat’s stomach.

FairCat Sensitive

FairCat Sensitive

with  psyllium seed husks & fennel

8 x 85g for 10.32 €

FairCat Beauty

FairCat Beauty

with aloe vera & hemp oil

8 x 85g for 10.32 €

FairCat Fit

FairCat Fit

with Vitamin C+E

8 x 85g for 10.32 €

FairCat Safe

FairCat Safe

with insect protein

from 3.79 €


Diagnosing a food allergy is done using a so-called exclusion diet. This process takes place over a period of at least 6 to 12 weeks and involves feeding the cat exclusively one source of protein and one source of carbohydrate. This applies to snacks too. These should contain the same source of meat as the main food. At the end of this period, once symptoms have subsided, an additional source of protein is introduced. If this results in an allergic reaction, it proves that your cat is allergic to the second source of protein or has an intolerance that is triggered by this ingredient. An exclusion or elimination diet should only be conducted in consultation with your vet.

You can also get a blood test done at your vet to diagnose food allergies. However, this kind of test is generally less informative as it only shows which food ingredients probably will not trigger an allergic response from your cats immune system. A negative result means it is highly likely the relevant food will be tolerated. A positive result (common for beef and grains) simply shows that the cat has previously encountered this food. The detection of antibodies does not necessarily indicate an allergy.
Since many illnesses have similar symptoms to food intolerances or allergies, other conditions need to be ruled out first.
Making a diagnosis without investigating the cause carries the risk of overlooking something else. Ultimately, an exclusion diet is the only way to accurately identify potential allergies and their triggers.


When feeding a cat with a sensitive stomach, choosing the right cat food is crucial. The food should contain no more than 1 or 2 easily digestible protein sources. 

With just 1 or 2 protein sources, the body is not overburdened with too many different types of protein. For sensitive and allergic cats, a bland diet is recommended. A single protein has a low allergenic potential and minimises the likelihood of an allergic reaction. When changing food, you should choose a protein source that you know your cat has not reacted to previously. If you identify a substance that your cat cannot tolerate, it may be enough to simply ensure this substance is not included in the food and e.g. to avoid milk products.

If that is not enough, you will need to change the food variety.

We believe transparency is key

This is evident in our cat food range, which provides a detailed description of all ingredients. Our food is based exclusively on high-quality ingredients and the recipes are low in allergens and gentle on the stomach. The food contains just a few carefully selected sources of protein. Our food varieties are generally ideal for cats with a sensitive stomach.

Insects are becoming increasingly popular in food! And for good reason: in pet food they represent a sustainable, alternative protein source, which provides essential amino acids, healthy fatty acids and minerals. Insects are ideal for cats and dogs with food allergies because this is a relatively rarely used source of protein. This ingredient plays an important role in our FairCat Safe dry food.
We use larvae from black soldier flies. These are sourced from small European farms, who we work with closely. This allows us to ensure high-quality food standards and short transportation distances. This approach is also helping us develop an interesting alternative to conventional meat for human nutrition in Europe.
Using insects brings lots of benefits – both in terms of health and for the environment.

  • The use of insects in cat and dog food can contribute to climate protection because the production methods are significantly more environmentally friendly.
  • Compared to rearing pigs, insect breeding causes much lower levels of ammonia gas discharge and thus less soil contamination.
  • The production of 1 kg beef requires around ten times as much land as the production of 1 kg insect protein

There are many causes and triggers for food intolerances in cats. However, if you recognise the specified symptoms in your cat, you should contact your vet immediately. Whether it is a food allergy or an intolerance – it can be a shock when your cat is diagnosed. Deep breathing is required! Luckily, there are now lots of options to give your cat a healthy diet that lacks nothing in terms of taste or enjoyment. Alternative gentle protein sources, such as insects or chicken, may be suitable solutions for your cat, so it can make the most of every one of its 9 lives. And your cat can help with climate protection too. At Green Petfood we are focused on sustainable, ethical farming for our animals. Meat in the pet food sector normally comes from conventional farms. But there are animal-friendly alternatives! Whether it’s chicken or black soldier flies– our focus is always on dignity and respect for the animals. And your cat can taste the difference too!