Red Dye Allergy in Cats

Red Dye Allergy in Cats - Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost

What is Red Dye Allergy?

It can be difficult to diagnose red dye allergy because there are rarely any visible signs of an allergic response. When it is definitively diagnosed, it is treatable. Dermal or skin allergies will most likely be present. These reactions can be symptoms of other allergies or intolerances and this will make it harder for your veterinarian to determine that red dye is the culprit. In extreme cases, your cat can suffer from anaphylactic shock which can be fatal if not immediately treated. 

Once red dye allergy has been diagnosed in your cat, it will be essential that you avoid all products that contain red dye. This means you will have to do some research to find the best food and treats for your cat.

Red dye allergy in cats is also known as red 40 allergy in cats. This means that your cat is unable to digest red dye or food coloring #2 or #40. Red dye can also be referred to as carmine or cochineal extract. Red dye is most commonly used to prepare, preserve or add coloring to food. Red dye allergy in cats is actually food intolerance since no allergic reaction occurs.

Symptoms of Red Dye Allergy in Cats

When your cat is suffering from some form of an allergy or ailment you will notice that they are acting oddly or they have physical symptoms that need to be quickly addressed. Be sure to contact your veterinarian for an appointment when you notice anything that is off about your cat so a quick diagnosis can be made and treatments begun. Symptoms of red dye allergy in cats include:

  • Itching
  • Redness and/or swelling of the skin
  • Hives or rashes
  • Angioedema, or the swelling of deeper skin layers
  • Diarrhea
  • Bloating
  • Excess gas
  • Vomiting
  • Difficulty breathing
  • Fever
  • Sneezing 
  • Anaphylactic shock
  • Joint pain
  • Lack of appetite

Causes of Red Dye Allergy in Cats

Red dye is not just found in food sources. It can be found in numerous other sources including toothpaste, medications and vitamin supplements. Red dye is extracted from a beetle and then processed into dye. Your cat’s commercial food could contain red dye or red #40. Read labels carefully if your cat has been diagnosed with this allergy. Avoid any foods, treats and supplements that contain dyes, especially red dye.

Diagnosis of Red Dye Allergy in Cats

Red dye allergy is very difficult to diagnose in cats. The symptoms that usually present are very similar, if not that same, as other conditions or allergies. This makes pinpointing the exact cause of your cat’s illness much harder for your veterinarian. 

Your veterinarian will begin by asking for your cat’s medical history, this will include any known allergies. They will also need to know your cat’s diet and environment. A physical examination will be conducted including a complete blood count, biochemistry panel, urinalysis and fecal exam.

Your veterinarian may need to conduct an elimination diet test to try and determine what is causing the problems. This can take several weeks before your veterinarian finally finds the red dye allergy.

Treatment of Red Dye Allergy in Cats

Once your veterinarian has definitively diagnosed red dye allergy in your cat they can discuss treatment options with you. Your veterinarian will treat the symptoms that have presented. Steroids may be recommended to stop the itching and reduce any swelling. Anti-itch cream can be used if your cat is suffering from extreme itching. Antihistamines may help your cat’s symptoms.

All medications should be administered as prescribed. If you have any questions regarding your cat’s medications direct those to your veterinarian. 

If your cat is suffering from gastrointestinal problems, your veterinarian may recommend an anti-diarrhea medication. In general, digestive upset will alleviate itself once the red dye has been excreted from the body. 

Anaphylactic shock needs to be treated immediately using epinephrine or even adrenaline. This is usually injected by your veterinarian. It can be lethal if not treated immediately. Your veterinarian may recommend keeping your cat in the hospital after they have suffered from anaphylactic shock for monitoring and to provide supportive care. Supportive care will include intravenous fluid therapy, oxygen therapy and possible nutritional therapy.

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Recovery of Red Dye Allergy in Cats

Once it has been determined that your cat is suffering from red dye allergy, it will be essential that you be very aware of the ingredients in your cat’s food, treats, vitamins and any other product that your cat will ingest or possibly ingest. You can ask your veterinarian to recommend food and treats that are dye free or at least do not contain red dye.

Red Dye Allergy Questions and Advice from Veterinary Professionals


Russian Blue




2 Years


4 found this helpful


4 found this helpful

My pet has the following symptoms:
Bumps On Skin
Why does my cat have bumps all over its body? My 2 year old russian blue has actue onset of small patches of bumps in the last 2 days. The areas of concern are sacral, behind the ears, and under her chin. She has a red food dye allergy but has not ingested any that we know of. Could this be a reaction to an internal or external source? I use a cat hair brush on her frequently which gets a lot of fur off at one time, but she never exhibits signs of pain as if I am brushing to roughly. She does itch at the spots, and her mannerisms have not changed. No apparent stress has been added or taken, and food and water have remained constant. We have not gone anywhere out of the ordinary to collect extra allergens or pathogens, and out laundry soap has remained the same

July 18, 2018

4 Recommendations

Cats may be allergic to practically anything and even may develop allergies to things they’ve been in contact with their whole life; so it can be difficult to narrow in on a specific allergen even if there is nothing new in the home. The bumps may be from allergies, but also from other causes like skin infections or parasites; apart from bathing her and taking usual precautions you should visit your Veterinarian for an examination and possible skin scraping (if indicated) to narrow in on a cause. Regards Dr Callum Turner DVM

July 19, 2018

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