The worst ingredients in dog food fall into three groups: synthetic preservatives (BHA, BHT, ethoxyquin), texture and appearance additives (propylene glycol, artificial colors, added sugar), and animal ingredients so vague you cannot tell what animal they came from. Below are the twelve I check for by name, the same list you would end up checking for yourself if you read as many bags as I have, what each one is doing in the bag, and the ingredient you want to see in its place. This is the field guide; the policy behind it, and why some famous villains are missing, is in the ingredients The Truva Standard rejects.
Synthetic preservatives
1. BHA (butylated hydroxyanisole)
A synthetic antioxidant that keeps fats from going rancid. The National Toxicology Program has listed BHA as "reasonably anticipated to be a human carcinogen" since 1991, based on animal studies, and notes its use in food and animal feed.1 The doses in those studies are far higher than anything in a bowl, so treat this as precaution rather than proof. Look for instead: mixed tocopherols, which is vitamin E doing the same job.
2. BHT (butylated hydroxytoluene)
BHA's chemical cousin, usually listed right next to it. BHT is not on the NTP list, and I am not going to pretend the evidence against it is stronger than it is. The reason to skip it is simpler: it is a cost decision. A brand that pays for tocopherols is telling you something about how it makes other decisions. Look for instead: mixed tocopherols, rosemary extract, or both.
3. Ethoxyquin
Legal in animal feed at up to 150 parts per million, and the FDA requires it to be declared on the label as "Ethoxyquin, a preservative" or with wording about protecting carotene and vitamins A and E.2 You will see it most in fish based kibble. If a fish food does not list it, it is worth asking the brand whether their fish meal supplier used it before it arrived, since the label reflects what the manufacturer added. Look for instead: fish foods that name the preservative in the fish meal, not just in the finished product.
Texture and appearance additives
4. Propylene glycol
A humectant that keeps semi moist food and soft treats from drying out. The FDA prohibits it in food for one companion species because it "has not been shown by adequate scientific data to be safe for use" there.3 It is allowed in dog food, and the evidence in dogs is different, so this is not a poison alarm. It is a signal that the product is engineered for shelf texture rather than nutrition. Look for instead: foods and treats that are dry, freeze dried, or refrigerated, and that stay soft because of moisture, not additives.
5. Artificial colors (Red 40, Yellow 5, Yellow 6, Blue 2)
Approved for use, like other additives in animal food that must be either approved or generally recognized as safe.4 Legal is not the same as useful. The dye is for the shopper. It does nothing for the dog, and a kibble that needs to look like little orange carrots to sell is showing you its priorities. Look for instead: uniformly brown food. Brown is what cooked meat and grain look like.
6. Corn syrup, sugar, and other added sweeteners
Most common in soft treats and semi moist food. Sugar is there to make the product taste like something the dog would not otherwise choose. Dogs have no requirement for it. Look for instead: treats whose sweetness, if any, comes from a whole food you can name, like sweet potato or blueberries. Our treats and chews collection screens for this.
Animal ingredients you cannot identify
7. "Meat" and "meat by-products"
The problem is the missing species, not the word by-product. AAFCO defines meat by-products as the clean, non-rendered parts other than meat from slaughtered mammals, including lungs, spleen, kidneys, brain, liver, and blood.5 Tufts' nutrition service notes that these organ meats often provide more nutrients than muscle meat per weight.6 "Chicken by-products" is honest and often nutritious. "Meat by-products" could be a different animal every batch. Look for instead: a species in front of every animal ingredient.
8. "Animal fat"
Same issue. Fat carries flavor and calories, and unnamed fat can come from anywhere the price is right. Look for instead: chicken fat, beef fat, salmon oil. Named, and ideally preserved with tocopherols.
9. "Animal digest"
A palatability spray made by breaking down animal tissue with enzymes or acid. It is what makes many kibbles smell the way they do. Unnamed, it tells you nothing about the source. Look for instead: "chicken digest" or, better, a food that does not need a coating to get eaten.
10. "Natural flavors" with nothing else specified
A catch-all. It is not dangerous, and in a food where every other ingredient is spelled out, it is a small thing. In a food that is already vague about its protein and its fat, it is one more door closed. Look for instead: labels that say what the flavor is.
Label tricks rather than ingredients
11. Ingredient splitting
Ingredients are listed by weight, and Tufts' nutrition team points out that ingredients from the same source can be split into components so each lands lower on the list.7 Rice flour, rice bran, and brewers rice are one crop in three costumes. Add them together before deciding what the food is mostly made of. Look for instead: a list where the named protein still leads after you have done the addition. The math is in how to read a dog food label.
12. "Fairy dust" ingredients after the salt
Blueberries, kale, and turmeric listed after salt and the vitamin premix are there in amounts Tufts calls "fairy dust," included solely for marketing.7 Not harmful. Just not worth paying extra for. Look for instead: if you want your dog eating blueberries, buy blueberries.
What is not on this list, on purpose
Corn, wheat, and rice. Tufts is direct that the vast majority of dogs are very efficient at digesting and using nutrients from grains, and that many grain free foods swap in refined potato or tapioca starch with fewer nutrients and less fiber.6 A food that is mostly grain and barely any meat is a different complaint, and the protein number will show it; see how much protein a dog needs. Named by-products are not on the list either, for the reasons above. And synthetic vitamins are how a food becomes complete, not a flaw. Knowing the difference between the two is the whole point of reading the list yourself instead of trusting the front of the bag.
When to call the vet
None of these twelve will hurt a healthy dog from one bag, so a bad label is a reason to switch, not to panic. Call your vet if a food change comes with vomiting or diarrhea that lasts more than a day or two, new itching, or a dog that stops eating. Bring the bag. The lot number on it matters if the problem turns out to be the food and not the ingredient.
Sources
- National Toxicology Program, "Butylated Hydroxyanisole, Report on Carcinogens, Fifteenth Edition," 2021. ntp.niehs.nih.gov (PDF)
- U.S. Food and Drug Administration, "Labeling and Use of Ethoxyquin in Animal Feed," accessed 2026. fda.gov
- Electronic Code of Federal Regulations, "21 CFR 589.1001," current. ecfr.gov
- U.S. Food and Drug Administration, "Pet Food," accessed 2026. fda.gov
- AAFCO, "Frequently Asked Questions," accessed 2026. aafco.org
- Tufts Cummings School of Veterinary Medicine, "Nutrition FAQs," accessed 2026. vet.tufts.edu
- Tufts Cummings School Clinical Nutrition Service, "Why you shouldn't judge a pet food by its ingredient list," 2016. Petfoodology