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What is Fish Allergy?

Fish is a food that is frequently utilized as a healthy source of protein for felines, although in some cases it can cause dangerous levels of contaminants like mercury to build up in your cat’s system. Some cats may also develop an allergy to fish or shellfish, causing unsightly and uncomfortable skin conditions. In order to reliably determine the proper allergen that is affecting your pet, an elimination diet may be required. This can be time-consuming but is frequently necessary in order to deduce which ingredient is causing the reaction.

Fish and seafood are common ingredients in food and treats that are formulated with cats in mind. For cats who develop an allergy to this food, it can cause an uncomfortable skin condition.

Symptoms of Fish Allergy in Cats

A food intolerance often accompanies and sometimes precedes a full-blown allergy to the food. The intolerance generally presents as gastrointestinal distress and gurgling sounds from the digestive system. Symptoms of food allergies generally start on the head and neck on felines and can include signs such as:

  • Acute moist dermatitis
  • Crusty papules
  • Hair loss
  • Itchy skin
  • Lesions on skin


Food Allergy

An allergy is a response by the body’s immune system to defend itself against something that it perceives as a threat. An allergic reaction from food doesn’t happen the first time an individual is exposed to the ingredient but rather after repeated ingestions. Any food is capable of finding an allergic reaction, but certain ingredients, such as beef, dairy, fish, and eggs tend to cause allergies in felines more often than others.

Food Intolerance

While a food allergy is the immune system responding to a perceived threat, an intolerance to a food has no immune involvement. An intolerance to a food type is more likely to cause a gastrointestinal response than allergies do. Further symptoms, such as gurgling sounds from the digestive system or a change in the consistency or color of the stools are also customary with a food intolerance.

Causes of Fish Allergy in Cats

Allergies, including food allergies, are due to an abnormally intense defensive response to a protein that the immune system views as an invasive substance. It is estimated that around 60-70% of our immune system cells actually reside in the digestive system, and the same applies to our felines. The process of digestion is designed to break down our foods into amino acids, the smallest parts they can be broken down into. These amino acids are then absorbed by a type of immune cell called an enterocyte, specialized white blood cells, and then transported into the bloodstream. When proteins are only partially broken down, the enterocytes see the fragments of food as intruders rather than nutrients, and they attack. Over time the reaction of these cells becomes more and more aggressive, and the symptoms intensify. 

Although allergies can develop to any food, some foods are more likely to generate a reaction than others. Frequent offenders for felines can include:

  • Beef
  • Corn
  • Dairy products
  • Eggs
  • Fish
  • Lamb 
  • Seafood
  • Soy
  • Wheat gluten

Diagnosis of Fish Allergy in Cats

The symptoms related to allergies in felines closely mimic other disorders such as mites or bacterial infections, and will typically prompt the veterinarian to collect skin scrapings as samples to be examined under a microscope, a process known as cutaneous cytology. When the skin cells don’t reveal any other micro-organisms or problems, then an allergy may be suspected. Although both serum and intradermal testing are available for cats with allergies, they are not as reliable for detecting allergies that are related to food. The veterinary gold standard for diagnosis of food allergies is the elimination diet. This diet is implemented by changing the cat’s daily diet to either a limited ingredient or hypoallergenic commercial cat food, or in some cases, to a diet of unseasoned human food. In choosing the proper diet for your allergic cat, novel ingredients are generally required.

Novel ingredients can include any proteins and carbohydrates that are not currently used in the cat’s current diet and preferably ones that have never been introduced. It is of particular importance to check for additional ingredients in commercial diets if you suspect a fish or seafood allergy as fish meal and fish oil are often added to food to increase the amount of omega-3 vitamins. Once signs of the allergy have been eliminated, new ingredients can be reintroduced into the diet one at a time, to uncover which one is triggering the reaction.

Treatment of Fish Allergy in Cats

Revealing the specific allergen that is bothering your pet may require several weeks on the elimination diet, and during this time your cat may continue to experience residual symptoms of the allergy. Corticosteroids are frequently recommended as a way to reduce swelling and antihistamines are often effective at calming itching sensations. Use of either treatment may mask the symptoms of the allergy, however, and this can make it more challenging to single out which ingredient in your cat’s diet is triggering the reactions. Because of this, many veterinary professionals prefer to administer the elimination diet before adding these types of medications to the regimen.

Secondary skin infections are a common occurrence for cats that are experiencing the symptoms of allergies, and antibiotics are usually prescribed to combat and sometimes prevent this particular complication. Once the particular allergen has been defined, this ingredient should be completely eliminated from the cat’s diet and other supplements, including probiotics and non-fish based Omega-3 oils, are frequently recommended for all sorts of allergies as a support to the immune system. This will assist your companion’s body in handling any accidental exposure to allergens and in preventing the cultivation of new allergies.

Recovery of Fish Allergy in Cats

Food allergies are not curable, but symptoms tend to cease fairly rapidly when the allergen is eliminated from the animal’s diet. Any repeat exposure to the allergen can trigger a relapse, so caution should be taken in which treats and flavorings you offer your cat, particularly as fish oil and fish meal are frequently added to products that are not labeled as fish based. Unfortunately, if your feline has experienced an allergic response to one ingredient, then they are more likely to develop allergies to other ingredients as well. The approach to combat this situation varies within the veterinary profession, with some doctors advocating that your cat remain on a single source of food, while others maintain that a steady rotation of three of four foods with proteins is optimal.

Fish Allergy Questions and Advice from Veterinary Professionals

domestic short hair
13 Years
Mild condition
0 found helpful
Mild condition

Has Symptoms

Irritations and swelling of mouth

My car is on a prescription diet for thyroid issues. I was told I could introduce fish oil to help with her dander.
I did that and it seems as though she’s had an immediate reaction. Her lip area swole up with what looks like sores. She lets me touch them and is still eating and drinking normally. I have removed the fish oil. Can I give her Benadryl?

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
1993 Recommendations
For allergies in cats it is best to give 5mg of cetirizine one per day (you should consult with your Veterinarian first since antihistamines may have a negative effect on some cats with certain thyroid issues), obviously withhold the fish oil and think about alternatives as there are some plant based (seaweed derived I think) sources of omega oils. If the swelling doesn’t go down, visit your Veterinarian; other causes may be insect bites, self trauma or other allergies. Regards Dr Callum Turner DVM

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domestic short hair
8 Months
Moderate condition
0 found helpful
Moderate condition

Has Symptoms

Loose Bowel Movements
Loose Bowel Movements diarrhea

I got my cat a month ago from a pet cafe and she's had diarrhea since I've had her. She's been eating purina one salmon flavor at the cafe. After 2 weeks I took her to the vet and they tested her poop which came back negative for parasites, giardia etc. they gave me a dewormer and probiotic which she's done with. I switched her good to taste of the wild and it's been 1.5 weeks with no better results. I am stressed and need another opinion.

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
1993 Recommendations
There are various causes for diarrhoea and it may be that Elvira is stressed, other causes apart from parasites are infections, poisoning, colitis, dietary sensitivity among other causes. You should try moving to a restricted ingredients diet to see if there is any improvement; also there may be something in your home which is causing diarrhoea. Regards Dr Callum Turner DVM

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