Dangerous Preservatives

You may not know that cats are more sensitive to chemical preservatives than humans are, but in fact, cats are more sensitive than most animals. Although a person's immune system is usually effective in fighting an onslaught of chemicals and pollutants, a cat's will swiftly succumb to invaders in its body.

Many types of cat food contain chemical preservatives. There are several different types of preservatives to avoid; some are downright toxic to your cat. The best way to educate yourself about preservatives is to become a chronic label reader. By knowing what goes into your pet's food, it is easier to keep your pet happy and healthy.

The common chemical preservatives that you will most likely read among the ingredients in the cat food labels are:

  • Ethoxyquin
  • Sodium Nitrate / Sodium Nitrite
  • Propylene Glycol
  • BHA / BHT
  • Benzoic Acid / Sodium Benzoate / Potassium Benzoate

The FDA requires cat food manufacturers to list all contents of their products on the ingredient label in descending order by weight. If you see the presence of even traces of these preservatives in the cat food you are thinking about buying, you will do your cat a great deal of good if you skip that product and choose a healthier, safer alternative.


Ethoxyquin is a preservative used mostly in dry pet foods. It is commonly used as a pesticide spray for apple scale (a type of fungus that grows on apple skins) and as a rubber hardener. It is described in Hawley's Condensed Chemical Dictionary as "Hazard: Toxic by ingestion."

On a scale of 1 to 6, ethoxyquin has a toxic rating of 3. To give you an idea of the toxicity scale, a 6 means 7 drops or fewer causes instant death. No more than 5 ppm (parts per million) of ethoxyquin are allowed in human food, but there can be up to 150 ppm in pet food. Ethoxyquin has been linked to allergic reactions on the skin (such as rashes and inflammation), infertility, birth defects and behavioral disorders in animals.

Symptoms of ethoxyquin poisoning in cats include:

  • Depression
  • Skin irritation
  • Liver damage
  • Convulsions
  • Coma

Read the labels on the food you are buying for your cat. If the ingredient list states it has been preserved with ethoxyquin, avoid it.

Sodium nitrite/sodium nitrate

Sodium nitrite is used to give cat food that red, meaty look and to preserve freshness (which is more for an owner's benefit than a cat's). Sodium nitrite and sodium nitrate, which is also used to preserve freshness, are considered carcinogenic in animals when they combine with amino acids to form nitrosamines. These can cause chemically induced cancer.

Animal ingestion of sodium nitrate/nitrite is comparable to cigarette smoking in humans. Nitrosamines cause stomach cancer, as well as acute liver damage. In addition, sodium nitrate depletes vitamin A, an essential vitamin for cats. Some animals are also allergic to sodium nitrite/nitrate.

Symptoms include:

  • Dizziness
  • Panting and wheezing
  • Lack of appetite
  • Nausea

To avoid sodium nitrite/nitrate, check the labels on canned and semi-moist foods. Nitrite/nitrate-free foods may not last as long as treated food, but they may prolong your cat's shelf life.

Propylene glycol

Propylene glycol is a humectant, or thickener, that is used mostly in semi-moist cat foods. This preservative is suspected of causing tooth decay, obesity and cancer.

Propylene glycol is known to create a red blood cell disorder in cats called "Heinz Body Formation." This disorder is a form of anemia that reduces blood cell survival time. It also renders blood cells more susceptible to oxidative damage. In other words, your cat assimilates less oxygen than he needs. Symptoms of Heinz Body Formation include:

  • Pale, whitish gums
  • Weakness
  • Listlessness
  • Loss of appetite
  • Vomiting

To avoid propylene glycol, check the label of your cat food.


BHA and BHT are used primarily as preservatives in dry pet food. They prevent the fat with which the food is sprayed from turning rancid. BHA and BHT are quite similar; you might call them "chemical cousins."

BHA is suspected of causing liver and kidney dysfunction in cats, as well as behavioral and reproductive damage and squamous cell carcinomas (more commonly known as skin cancer). Squamous cell carcinomas are among the most lethal and fastest-spreading types of cancer. Animals with light-colored fur tend to be affected the most quickly.

BHT promotes urinary bladder carcinogenesis, and it could be a promoter of thyroid carcinogenesis as well. Additional effects include stomach cancer, liver and kidney damage.

Symptoms of BHA and BHT damage to your pet's kidneys and liver are:

  • Increased water consumption
  • Decreased urination
  • Weight loss
  • Bloody urine
  • Lethargy
  • Diarrhea
  • Vomiting
  • Jaundice
  • Tongue discoloration

Again, check the ingredients label for these preservatives. BHT, like ethoxyquin, is a very popular preservative.

Benzoic acid, sodium benzoate, potassium benzoate

Benzoates are the most widely used food preservatives in the world. Sodium benzoate is widely used in beverages, syrups, margarine, sauces, preserves, pastry and pie fillings, salad dressing, prepared salads and in storage of vegetables.

This substance, although used safely as a preservative in human food, is rarely used in cat food because it causes adverse reactions in cats - it makes them highly aggressive. Benzoates are common in human foods that you may want to share with your cat or that he may accidentally eat, so take precautions. Keep benzoate-preserved human food away from your cats.

Symptoms of benzoate poisoning include:

  • Loss of balance
  • Muscle tremors
  • Aggressiveness and rage
  • Blindness
  • Increased pain sensitivity

Benzoic acid is frightening because of its unique effect on cats-it can turn a gentle cat into a raging beast.

If you suspect benzoic acid poisoning, approach your pet with caution. Wrapping a towel around your hands will prevent injuries if your cat lashes out at you.