Allergy in Cats

An allergy is the body’s own reaction to normally harmless substances (allergens or antigens) in which the body forms certain protective proteins, so-called antibodies. This antigen-antibody reaction can ultimately lead to various secondary reactions which, in addition to harmless skin inflammation, can also lead to life-threatening situations. In principle, any cat breed can be affected by an excessive immune reaction and this can occur spontaneously at any time.

In order to better understand how an allergy can develop in cats and which diseases result from it, allergic reactions are divided into the following 4 types:

Immediate type:

  • Usually occurs within a few seconds or minutes;
  • Is the most common type in cats;
  • Formation of IgE antibodies, which lead to a sharp increase in histamine in the body;
  • Example: allergic asthma.

Cytotoxic type:

  • Starts within a few hours;
  • Links between cell-bound antigens and the body’s own antibodies (immunoglobulin G, IgG) lead to the formation of immune complexes which, in the further course, cause the destruction of body cells such as blood platelets (thrombocytes) or red blood cells (erythrocytes).

Arthus or immune complex type:

  • Occurs within a few hours;
  • Also formation of immune complexes between the antigens and antibodies, but this reaction is not only cell-bound but also on freely mobile antigens;
  • Example: allergic inflammation of blood vessels (vasculitis).


  • Only occurs after several hours or days;
  • Certain immune cells (T lymphocytes) attract other immune cells to the allergen and cause inflammation there;
  • Example: transplant rejection after an operation.

Environmental allergy (atopy)

Like us humans, cats can also develop an allergy to various environmental allergens such as pollen or house dust. The latter usually causes an allergic skin inflammation year-round, while a pollen allergy typically occurs seasonally. Further examples of other air allergens are mold spores or fragrances, which can be found in cat litter.

Flea saliva allergy

Allergic reactions in cats are particularly often caused by a flea infestation, more precisely by flea saliva. Typically, the affected cats show small inflammatory nodules on their backs, which is also known as “miliary dermatitis”. Increased licking due to severe itching can lead to bacterial or fungal secondary infections worsening the skin inflammation.

Feed allergy

In addition to a flea saliva allergy, food allergy is also frequently observed in cats.

This can develop spontaneously and, in addition to itching, leading to vomiting and diarrhea. It is important to differentiate a feed allergy from a feed intolerance, as this is not caused by an immune-mediated hypersensitivity.

Cat eosinophilic granuloma complex (EGK)

No exact cause is known for this cat-specific, allergic disease. However, it is assumed that a flea infestation, for example, can have a triggering effect. The disease leads to strong defense reactions of the immune system, which lead to inflammatory nodules (eosinophilic granulomas) and sometimes severe pain, especially in the mouth area. In addition to inflammation of the mucous membranes, inflammation can also occur in other skin regions such as the head or the inner thighs.

Cat allergy symptoms

The clinical picture of allergy in cats is very variable and can include the following symptoms:

  • Severe itching: rubbing against objects and scratching;
  • Hair loss (alopecia);
  • Gastrointestinal complaints: nausea, vomiting, diarrhea;
  • Secondary bacterial infections: skin inflammation and other organ inflammation;
  • Allergic asthma and anaphylactic shock: sudden danger to life due to shortness of breath.


If your cat shows signs of allergy, you should see your veterinarian. This can narrow down the allergens by means of exclusion diagnostics and prevent the symptoms from worsening. During the owner survey (anamnesis), he asks for important information about the detection of possible allergens. For example, a flea saliva allergy is very unlikely if the cat is given effective flea prophylaxis throughout the year.

On the other hand, a seasonal increase in allergic relapses is a sign of a pollen allergy.

The anamnesis is followed by a general clinical examination, which provides information about the general health status of the cat. For example, breathing, pulse, and heartbeat as well as the internal body temperature are measured using a rectal thermometer.

If the cat does not show any drastic changes in the vital parameters, a special examination can be started.

The aim of the special examination is to find out the cause of the allergy using specific tests. A feed allergy is diagnosed, for example, by a so-called elimination diet, an abrupt and long-term change of feed. If the cat’s symptoms improve, a positive result can be assumed. However, to confirm the suspicion, the cat can be fed the old food again. If the cat shows clinical signs again, a food allergy is very likely.

If the allergens cannot be identified by exclusion diagnostics, the veterinarian can use more specific tests such as the skin test (intradermal test) or blood test (serum test). These can specifically detect allergens, although the results are unfortunately not always reliable.


The therapy of an allergy in cats depends on the cause and the extent of the clinic.

The following treatment measures may be necessary to increase the quality of life or even the probability of survival of the affected cat:

  • Antiallergic drugs (e.g. antihistamines);
  • Immunosupressants (e.g. cortisone or atopica);
  • Anti-inflammatory shampoos or spot ons;
  • Secondary infections: antibiotics (after resistance test) or antimycotics;
  • Desensitization (desensitization) through lifelong administration of individually prepared allergen serums.

Allergies in cats are very common and tend to be mild. In a few cases, however, severe anaphylactic shocks can occur, which can be fatal due to shortness of breath. It is therefore very important to prevent further allergic flare-ups.


Allergies can arise at any time. However, in order to reduce the risk of developing an allergy or further allergic relapses, the following prophylactic measures can be observed:

  • Avoid contact with known allergens;
  • Regular flea prophylaxis (e.g. spot ons or collars);
  • Desensitization.
Mary Allen

Written by Mary Allen

Hello, I'm Mary! I've cared for many pet species including dogs, cats, guinea pigs, fish, and bearded dragons. I also have ten pets of my own currently. I've written many topics in this space including how-tos, informational articles, care guides, breed guides, and more.

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