Bully Stick Diarrhea: Causes and What to Do Next

By INVIROX Training Team · Published 2026-11-02 · 10 min read

Can bully sticks cause diarrhea?

Yes, they can, and it is one of the most common things owners report after a dog's first bully stick. It is rarely a sign that the stick was bad. More often it is simply a lot of dense, unfamiliar food arriving in a stomach that was not expecting it.

A bully stick looks like a toy, but it is food. When Tufts University researchers measured retail bully sticks for a 2013 study in the Canadian Veterinary Journal, an average 6-inch stick held about 88 calories. That is roughly 9% of a 50-pound dog's daily calories, and about 30% for a 10-pound dog. A small dog that finishes a whole stick in one afternoon has eaten close to a third of a day's food in one sitting, all of it a single new protein.

Board-certified veterinary nutritionists writing in Today's Veterinary Practice recommend keeping treats to no more than 10% of a dog's daily calories. A whole bully stick can blow past that for a small or medium dog, and a sudden jump in rich food is a classic trigger for loose stool.

So the first question is not what was wrong with the stick. It is how much of it your dog ate, how fast, and whether this was the first one.

The five usual causes, side by side

Most cases fall into one of five patterns. The clues in the middle column help you work out which one you are looking at, and the right-hand column tells you what to do about it.

The first two are by far the easiest to fix and the ones most owners are dealing with. The last two are the ones you must not miss, so the sections below cover each in turn.

Too much, too fast: the most common reason

The pattern owners describe again and again goes like this: a new bag arrives, the dog is thrilled, the stick vanishes in twenty minutes, and the next morning there is diarrhea. The dog is otherwise happy, eating and full of energy.

That is a quantity problem rather than a quality problem. The stick softens as your dog chews it, and a fast chewer can take in several inches in one session. Add that to a normal meal and the total is more food than usual, richer than usual and new.

• Split one stick across several short sessions instead of giving it all at once.
• Take the stick away after 5 to 10 minutes at first, and put it back in a sealed bag.
• Trim the next meal slightly on days your dog has a chew, so the total food for the day stays the same.
• For small breeds, use part of a stick per session. The calorie share is much higher for them.
• Use a holder or a thicker stick if your dog bites off big pieces rather than gnawing.

→ Related reading: bully stick calories by length and dog weight

A new protein, or a beef allergy?

Any new food can unsettle a dog's stomach for a day or two while the gut adjusts. That alone does not mean your dog cannot have bully sticks. It usually means the first introduction was too big.

A food allergy is different. It tends to come back every time the food is given, even in small amounts, and it often shows on the skin as well as in the stool. Beef is worth thinking about here. In a 2016 review in BMC Veterinary Research, beef was the most commonly reported food allergen in dogs with food-related skin reactions, involved in about a third of cases, ahead of dairy and chicken.

Signs that point toward an allergy or intolerance rather than a one-off upset:

• Loose stool returns each time, even after a careful, slow reintroduction.
• Itchy skin, licking or chewing at the paws, or repeated ear problems.
• Your dog already reacts to beef-based food or other beef treats.
• Gas, soft stool or vomiting that tracks with beef rather than with the amount.

Bully sticks are a single ingredient, which actually helps here: there is only one thing to suspect. If you think beef is the problem, stop beef chews and talk to your vet. The usual next step is a structured food trial, which needs a vet's guidance to give a clear answer.

When contamination is the cause

Bully sticks are dried, not sterile. In the same 2013 Tufts study, researchers found bacteria on several of the 26 sticks they tested, including E. coli on 7. FDA recall notices also show that bully stick products are occasionally recalled for Salmonella: one lot of a 7-inch bully stick 3-pack in 2018, and four lots of a bully bites product in 2025 after an FDA sample tested positive. No illnesses were reported in either case, but both are reminders that it can happen with any brand.

In its recall notices, the FDA lists the signs of Salmonella in pets as lethargy, diarrhea or bloody diarrhea, fever and vomiting. People can be affected too, which is why the FDA advises washing and sanitizing your hands after handling pet treats.

Contamination is more likely to be the explanation when the diarrhea comes with fever, low energy, vomiting or blood, when it started with a stick that smelled wrong or looked slimy or moldy, or when someone in the home also feels unwell. In any of those cases, stop the sticks, keep the bag and the lot number, and call your vet.

→ Related reading: safe handling and storage rules for bully sticks

Diarrhea or vomiting after a swallowed piece

Sometimes the stomach upset has nothing to do with the stick's ingredients. It comes from the last piece of the stick going down whole. A large piece can sit in the stomach or move into the intestine, and the signs can look like ordinary tummy trouble at first.

Think about this cause first if the end of the stick went missing, if your dog gulped a large piece when you reached for it, or if the signs are more about vomiting and straining than loose stool.

• Repeated vomiting or retching, especially after drinking or eating.
• Straining to poop, or not pooping at all.
• A sore or tight belly, or your dog standing hunched.
• Low energy, hiding or refusing food.
• Small amounts of diarrhea with any of the signs above.

Those signs need a vet the same day. Do not try to make your dog vomit at home unless a vet tells you to.

→ Related reading: what to do if your dog swallowed the end of a bully stick

The first 24 hours, and the red flags

If your dog has loose stool after a bully stick but is bright, drinking and acting normally, these steps are a sensible start:

1. Stop all bully sticks and other chews for now, and pick up any half-chewed pieces.
2. Keep fresh water available and make sure your dog is drinking.
3. Keep the bag, or take a photo of the lot number and best-by date.
4. Note what you see: how often, how loose, any mucus or blood, and how your dog is acting.
5. Call your vet for advice before withholding food or giving any medicine or supplement. Puppies, small dogs and seniors can lose fluid quickly.
6. Wash your hands after cleaning up, and keep small children away from the mess and the treats.

A dog that has diarrhea once and then goes back to normal stools within a day, while eating and playing as usual, is the typical too-much-at-once case. A dog that seems unwell in itself, rather than just having loose stool, needs a vet.

How to reintroduce bully sticks safely

Once stools have been normal for a few days and your vet has no concerns, you can try again. The goal is to give your dog's gut a chance to adjust, and to give you clean information about whether the stick itself is the problem.

Dogs with a sensitive stomach often do best on this slow schedule long term: shorter sessions, a few days apart, and never a whole stick at once. If loose stool comes back twice even with this plan, that is useful information for your vet, and a sign to switch to a non-beef or non-edible chew while you find the cause.

It also helps to know exactly what you are giving. INVIROX bully sticks are one ingredient, grass-fed Brazilian beef pizzle with nothing added, so there is nothing else in the stick to suspect if your dog reacts. Whatever brand you use, keep the same one during a reintroduction so you are only changing one thing at a time.