4 Hidden Hazards of Dry Pet Food

Analysis by Dr. Karen Shaw Becker

hidden hazard of dry pet food

Story at-a-glance

  • Dry pet food, for all its convenience, is difficult to store in a way that preserves its nutritional value and freshness
  • One of the many potential problems with kibble is storage mites, which can contaminate your pet’s food and are also an allergen for many dogs and cats
  • Additional watch-outs for stored kibble include fat rancidity, mycotoxin contamination, and pathogenic bacteria
  • It’s important to take the necessary steps to preserve the safety and nutrient quality of any dry pet food you buy for your dog or cat
  • Since kibble is far from ideal pet nutrition for a long list of other reasons; for optimal health, feed your pet a minimally processed, high-quality animal protein and healthy fats and fiber, with low starch content

If you’re a regular visitor here at Mercola Healthy Pets, you know I’m not a fan of ultraprocessed pet food, particularly kibble, for many reasons. One of the problems with this convenience junk food that I’ve touched on, but not in any great depth, is the potential for storage mites, aka mold mites.

There are several species of storage mites, but the most common is Tyrophagus putrescentiae (it’s probably best not to watch this if you’re eating, just ate, or are about to eat!):

Not only is the idea of giving your furry family member food containing storage mites unappealing (to put it mildly!), not to mention biologically inappropriate, butthese little pests are also a common allergen for dogs and cats. In susceptible pets, ingestion can result in itchy inflamed skin, hair loss and recurrent ear infections.

Three Additional Watchouts When Buying and Storing Kibble

If you feed kibble, there are some things you need to know about what happens to it over time, and how to handle and store it once you get it home. The enemies of dry pet food include time, heat, sunlight, moisture and oxygen. The longer the food sits on a shelf (a store shelf or your pantry shelf), the greater the nutrient degradation.

#1: Rancid fats — As soon as a bag of kibble is opened, important dietary fats (e.g., omega-3 essential fatty acids) start to turn rancid.

As my friend and pet food formulator Steve Brown says, “A dog is the fat she eats,” meaning fats are critically important for dogs (and cats). Rancid fats (found in most ultraprocessed pet foods) are harmful, while healthy fats can be life-changing in terms of slowing and preventing many degenerative diseases (from kidney disease to cognitive decline).

Also, because kibble is processed multiple times and at extremely high temperatures, effectively killing all the nutrition in the food, manufacturers assume the finished product is grossly nutritionally deficient. That’s why the final production step involves spraying on a nutrient mix (and a palatability enhancer to make pets want to eat the stuff).

The sprayed-on synthetic nutrient mix typically contains cheap, feed-grade additives, vitamins and metal oxides and sulfates that can speed the oxidation of fats, ultimately resulting in rancid fats in a formula that may or may not be entirely safe to eat as little as a week after it was opened.

#2: Mycotoxins — Mycotoxins (derived from the Greek words for “fungus” and “poison”) are toxic chemical substances produced by certain types of fungi that infect crops, and U.S. pet food manufacturers are advised to monitor the quality of these ingredients going into their products.

A 2019 study found multiple types of mycotoxin contamination in 75% of grain-based dry dog food samples tested.1 The samples used in the study were from 5 different brands of commercially available dog food produced in the U.S. following U.S. guidelines for the manufacturing of dog food.

A total of 60 samples of grain-based dry and canned dog foods and grain-free dry and canned dog foods were analyzed for 11 different mycotoxins. From the study:

“Only dry dog foods containing grains had detectable mycotoxin contamination, and only mycotoxins that are products of the Fusarium genus were detected. Of the 12 dry dog foods containing grains that were analyzed, nine of the twelve had at least one detectable Fusarium mycotoxin.

For DON and fumonsin B1, 9/12 dry grain foods were above detection limits while 8/12 samples were positive for fumonsin B2 and 4/12 samples tested positive for zearalenone.

When considered by brand, at least one of the four Fusarium mycotoxins was found in each of the four brands of dry grain foods. For two brands … at least one of the three samples tested were positive for all four Fusarium mycotoxins.”

Common food sources of mycotoxins include:




Cottonseed and cottonseed oil

Barley (cereal)


Sugar cane and sugar beets (which also feed fungi)

Sorghum (found in a variety of grain-based products)

The above foods can be found in many commercially available pet food formulas. I recommend you study the ingredients in the food you buy your pet, and avoid brands containing grains or corn in any form, including corn gluten meal, whole grain corn, corn flour, etc. Also avoid formulas containing cereal grains like maize, sorghum, pearl millet, rice and wheat.

#3: Opportunistic bacteria — Despite what raw pet food alarmists would like you to believe, and even despite the FDA’s targeting of raw pet food producers, the vast majority of pet food recalls for pathogenic bacteria (e.g., salmonella, listeria, E. coli) and other contaminants involve kibble.

Unfortunately, the FDA removed the pet food recall lists from their website, so I’m not able to link to this information directly, but TruthAboutPetFood.com still maintains a vast database of all recalled pet foods.

Tips for Storing and Handling Kibble

Don't feed dry pet food past its exceptionally long expiration date. The older the food gets, the more it degrades and the greater the potential for contamination. For these reasons, I also recommend avoiding large-sized bags unless you can feed the whole bag in 30 days without overfeeding your pet(s). Buy small bags for small pets.

Check to make sure the food isn’t near (or past) its use-by date, and also ensure there are no tears in the bag. Since rancid fats are worse than no fats, I recommend buying formulas that do not contain added essential fatty acids (EFAs). Instead, add them fresh at mealtime. Sustainably sourced krill oil is an excellent choice.

Dry food that sits in a warm or humid environment presents a greater risk for rancidity, bacterial and fungal growth, and other problems, so it’s best to store most of it in the freezer, and remove just enough for one or two meals at a time. Kibble kept at room temperature (not recommended) should be in an airtight container that is washed frequently with detergent and hot (not warm) water.

When you open a new bag of kibble, don't pour the remainder of the old bag into it to avoid potential contamination of the new food. If you transfer the food to another container(s), you might want to write down the brand, variety, lot number and any other pertinent information in the event of a recall. I also recommend disposing of empty pet food bags immediately outside the house.

Why Not Consider Feeding Your Pet More Real Food?

The above issues with buying, storing, and feeding dry pet food only scratch the surface of the many problems associated with ultraprocessed kibble. Equally as concerning is the fact that most kibble is the most biologically inappropriate type of food on the market, and contains no identified real foods whatsoever.

My regular readers know that I recommend pet parents swap out as much high carb, low moisture dry food as possible with a minimally processed or raw nutritionally optimal, species-specific diet, which means food containing high-quality animal protein, moisture, healthy fats and fiber, with low to no starch content; basically the exact opposite of kibble when it comes to macronutrient appropriateness.

Longterm physiologic stress from consuming a lifetime of biologically inappropriate food translates into early disease and degeneration, not to mention a lifetime of GI, skin, metabolic and immune-related symptoms that decrease quality of life.

Throw in the consumption of massive amounts of unwanted heat-created foodborne toxins (AGEs) found in highly refined pet foods and the accompanying organ degeneration that ensues and it’s easy to see why the raw food category is one of the fastest growing segments in the pet food industry.

Well-formulated, commercial/store-bought minimally processed diets that are made with human grade ingredients are more expensive than feed-grade fast food (aka kibble) in the same way organic honeycrisp apples are three times the cost of anything on the dollar menu. This is why more and more people are choosing their only option to improve their pet’s diet: make the food themselves.

A nutritionally balanced raw or gently cooked homemade diet is my top choice for pets, but you should only attempt this if you're committed to doing it right. I have dozens of articles on this site that discuss the do’s and don’t’s of homemade diets, but in a nutshell, follow a recipe that was formulated to meet minimum nutritional requirements or use a nutrient blend specifically created for the recipe you’re using.

Most importantly, you don’t have to completely switch to an all-fresh food diet to reap the benefits of your pets consuming less processed nutrients. Every tablespoon of ultraprocessed food you can swap out for a less processed food means a step in the right direction.

To optimize your pet’s mealtime, be sure to incorporate a variety of fresh foods from your refrigerator into their diet, too, as meal toppers or treats. Diversifying your dog’s or cat’s real food intake means more food-based antioxidants, polyphenols and phytonutrients are available to benefit their microbiome, immune system and body.



By continuing to browse our site you agree to our use of cookies, revised Privacy Policy and Terms of Service.