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Cat Allergies: Signs, Triggers & Treatment

We hear so much about dogs suffering from food or contact allergies but what about our kitties? We spoke to
Dr David Horan, who shared his insights after 30 years spent working as a Veterinary Surgeon and Pet Educator/Trainer.

Is my Cat at Risk of Getting Allergies? 

All cats can be at risk for developing allergies. Cats that develop allergies have usually been exposed to substances - either airborne, in food, applied to their skin or caused by fleas - that they cannot tolerate. 

Cats which spend time outdoors may be more prone to flea and pollen allergies. Overweight cats and those exposed to cigarette smoke can develop asthma. 

General Signs of Allergies in Cats

  • Sneezing or wheezing
  • Coughing (if the cat has asthma)
  • Itchy skin or increased scratching 
  • Itchy, runny eyes 
  • Itchy ears and / or swollen ears 
  • Itchy back or base of tail (most commonly seen in flea allergies) 
  • Vomiting 
  • Diarrhoea 
  • Snoring - caused by an inflamed throat 
  • Paw chewing and or swollen paws 

What Can Cats be Allergic to? 

The following substances can cause allergic reactions in cats who are sensitive to them: 

✔️ Food
✔️ Fleas and flea-control products
✔️ Veterinary drugs
✔️ Human Medications and treatments
✔️ Cleaning products
✔️ Cigarette smoke
✔️ Fabrics
✔️ Rubber and plastic materials 

✔️ Plants (including trees, grass, weed, mould, mildew and dust pollens) 

How Common are Food Allergies in Cats? 

Cats who develop allergies to what they eat will commonly scratch at their head and neck as well as having gastrointestinal problems such as diarrhoea and vomiting. Food allergies may develop in cats of any age.

Note: If you know your cat is allergic to chicken, you should avoid feeding her any products containing chicken protein or fat.

It may seem natural to feed fish to cats because they generally love eating fish – it is tasty and aromatic. This is however not a natural extension – the domestic cat evolved from a desert dwelling ancestor some 9,000 years ago and hence had no access to fish. The habit of feeding fish to cats is the relatively modern result of the fishing and canning industries starting in the 1850s – canned fish as cat food being the by-product – usually containing fish species that were not suitable for the human food chain

Here are some of the problems with feeding cats on fish:

Oily Fish – deep sea species such as salmon and tuna can cause fat necrosis particularly in foreign or exotic cat breeds such as Siamese cats. The necrosis occurs primarily in the groin area and may need surgery to remove it. The best course is prevention by feeding anything else to these cats but not fish.

Raw Fish - should not be fed to any cats – fresh raw fish contains the enzyme thiaminase which destroys the vitamin Thiamine (Vitamin B1). Fresh fish should not be fed to cats. This can be avoided by cooking the fish – thus denaturing the enzyme.

Other foods to be careful of feeding to cats:

Liver – is highly addictive and detrimental to cats. Liver contains high levels of Vitamin A – feeding on Liver long term will cause ankylosing lesions in the cat’s joints resulting in a stiff gait and inability to groom, so called “Kangaroo Cat”. 

Treatment is simple but can be difficult to achieve – just stop feeding the cat on liver, the stiffness will resolve completely over a number of weeks. 

Cats and dogs may not tolerate cow’s milk – i.e. lactose intolerant - leading to GIT signs of diarrhoea. This can be avoided by feeding kittens on a low/no lactose alternative such a Womberoo or Di-Vetelact or feeding an adult cat on Whisker’s Cat Milk or Feline Natural Milk.


Just like dogs, cats can be allergic to flea bites. A flea allergy may only require a few flea bites to trigger intense itchiness for 2 to 3 weeks. Apart from an allergic reaction to the flea bite, the flea can transmit tapeworm (Dypilidium sp.) and if there are many fleas – anemia may result because fleas suck blood. It is important therefore to use flea control products. 

Veterinary Drugs 

Some veterinary drugs including Sulpha Drugs (BactrimTrimethoprim) may cause “Ropey” saliva in cats. 

Dog medications should be avoided as many medications can be tolerated by dogs and not cats. 

Human Medications and Treatments 

Human medications which are commonly found in the home must not be given to cats – these include Aspirin and Paracetamol – these can be fatal to cats. 

Likewise, “home remedies” such as Tea Tree Oil and all topical ointments should be avoided as anything that is applied to the cat’s skin will be ingested and can cause allergies or toxic results. 

Cleaning products 

Many cleaning products are toxic to cats. It is therefore important to rinse off these agents to neutralise them when you have a cat in the house. 

Good Scruff - Natural Cleaning & Odour Solutions
Cats are particularly sensitive to phenols and phenolic compounds, which can be found in some essential oils. The higher the concentration of the essential oil (i.e. 100%), the greater the risk to the cat. 

These are included in inexpensive disinfectants such as toilet cleaners and other cleaning products. Cats are usually exposed when they walk on the phenol contaminated area and they lick their paw or fur.

Note: do not use phenols around the cat litter box, or indeed at all.

Asthma in Cats

Cats suffering from asthma may show signs of difficulty breathing, wheezing, rapid breathing, coughing or hacking, open-mouthed breathing, or vomiting.

Sensitivity to environmental pollutants, pollen and stress can cause asthma attacks in cats. For short-term relief, your veterinarian may prescribe medications that will open up airways. For long-term treatment, corticosteroids may be used. 

Importantly, no cat should be exposed to cigarette smoke

What are Contact or Environmental Allergies for Cats?

Contact allergies may result from plants, cleaning products, fabrics and other materials. Signs of a contact allergy include itching and scratching, runny eyes, swelling of paws, ears and other skin areas.

Materials that cats can be allergic to carpet, plastic feeding and watering bowls as well as plastic / synthetic collars.

Common plant allergens include:

o Zebrina (Tradescantia zebrine)
o Inch plant (Callisia fragrans)
o Purple Heart (Tradescantia pallida)
o Turtle Vine (Callisia repens)
o Moses-in-a-cradle (Tradescantia spatheca)
o Scurvy Weed (Commelina cyanea)

How are Cat Allergies Diagnosed?

First step is to visit your Veterinary Surgeon – he or she will do a thorough clinical examination and may be able to diagnose what is causing the allergy.

If the vet cannot determine the cause, they may refer your cat to a veterinary dermatologist for an allergy test if your cat has itchy or irritated skin. The test of choice is an intradermal skin test, as blood allergy tests are not considered as reliable.

The ideal way to diagnose a food allergy is to feed your cat a prescription or hydrolyzed protein diet exclusively for a period of 12 weeks, this diet is free of potential allergy-causing ingredients. Your cat will remain on the diet until her symptoms go away. You then begin to reintroduce the old foods to see which ones might be causing the allergic reaction. This can take some time and commitment.

Importantly, many cats diagnosed with a food allergy will require home-cooked meals. This must be done in conjunction with your veterinarian as it requires a special protein and careful food balancing.

How can Cat Allergies be Treated?

The best way to treat allergies is to remove the allergens from the environment.

o Prevention is the best treatment for fleas. Start a flea control program for all of your pets before the season starts. Outdoor cats are not only be exposed to fleas but can also carry fleas inside to indoor pets. See your veterinarian for advice about the best flea control products for both your cat and the environment.

o Use a dust-free, unscented litter. Your cat might have an allergy to the chemicals in scented litter. You might have to experiment with different types and brands of litter until you find the best one for your cat.

o If dust is causing your cat’s allergic symptoms, clean and vacuum your pet's bedding once or twice a week, this includes carpets, curtains etc.

o Bathing your cat regularly may help relieve itching and remove environmental allergens and pollens from her skin; your vet will have advice regarding appropriate shampoos and conditioners for your cat. Remember frequent bathing can also dry out the skin. 

Note: Do this only if your cat is amenable to bathing!

o If your cat has a food allergy, she’ll need to be put on a prescription or hydrolyzed protein diet. After she has been diagnosed, your vet will recommend specific foods or a home-cooked diet.

What Allergy Medications are there for Cats?

If we cannot remove the substances that cause allergic symptoms from the environment, your vet may recommend the following medications:

o For airborne pollens, your vet may prescribe steroids to help control the allergy or even anti-allergy injections, which treat the allergy itself instead of just masking the itch.

o Antihistamines such as Benadryl can be used preventatively, before your cat is exposed to the allergen.

o Fatty acid supplements might help relieve your cat’s itchy skin. 

o There are many shampoos that may help prevent skin infection, which occurs commonly in cats with allergies. These often contain oatmeal, aloe and other natural products.

o There are several flea-prevention products that can be applied monthly to your cat’s skin, including Bravecto, Advocate, Profender, Frontline, Revolution Plus and even a new generation collar, Seresto, that lasts 8 months.

Remember – if you have any concerns regarding the health of your cat – consult your veterinarian as soon as possible.

Written by Dr David Horan, August 2020 for Australian Cat Lover (all rights reserved)

About the writer

Dr. David Horan (BVSc, MRCVS, BSc, PGDipEd, TAE40110) has been a veterinary surgeon for over 30 years and has worked for several years in Veterinary Emergency Practice at the NWAEC at Baulkham Hills, now part of ARH (Animal Referral Hospital). 

For almost 25 years David has chosen to work as a Mobile Vet in Sydney and all around the world, setting up the the first and longest running Mobile Vet Clinic in the Greater Sydney basin in 1996. In 2016 he set up, Sydney’s first and only dedicated pet end-of-life Consultancy and Caring In-home Euthanasia service.

He set up the Veterinary and Animal Care Centre at Richmond College in 1994 and lectured to Veterinary Nurses and Animal Technicians around the state with NSW TAFE for over 25 years, now retired.

David is the founder of - Global ÍPet Care Training and author of many pet and animal care manuals including Animal First Aid, Dog Care, Cat Care and Dog Health & Disease – all available through the website. There are also many unique and innovative courses available – including COVID Safe Online Practical Courses, Professional Video Training Apps and topical Webinars.

With half price special on all courses until 31 December 2020, now is the perfect time to take that Cat First Aid or Basic Cat Course.

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