Why Does My Dog Have Loose Stools? Common Causes, When to Worry, and What to Do Next

Dogs get loose stools and diarrhea from eating something they shouldn't have to food sensitivities, stress, infections, and even the quality of their everyday diet. Few things stop a dog parent in their tracks quite like discovering a messy surprise on the living room rug or watching their pup strain during a walk and produce something that barely qualifies as solid. It's stressful and never fun to clean up, but the good news is that most cases aren't serious.

That said, your dog's poop is actually one of the clearest windows into their overall health. When things go south, literally, it's your pup's body waving a flag that something is off. The trick is figuring out what.

Whether this is a one-time thing or you've been dealing with soft, mushy stools for days, this guide will walk you through the most common culprits, the warning signs that mean it's time for a vet visit, and how what goes into your dog's bowl plays a much bigger role than most pet parents realize.

What Are the Most Common Causes of Loose Stools in Dogs?

The most common causes of loose stools in dogs are dietary indiscretion (eating something they shouldn't), sudden food changes, stress, food sensitivities, low-quality ingredients in their diet, infections, and medications. Dog diarrhea rarely has a single dramatic cause. More often, it comes down to one or a combination of these everyday triggers.

Could my dog have eaten something they shouldn't have?

Dietary indiscretion, a.k.a. "they ate something questionable," is the number one cause of sudden loose stools in dogs. Counter-surfing, garbage-raiding, snacking on something suspicious at the park - if your dog got into something outside their normal diet, their digestive system is going to let you know about it.

Most cases resolve on their own within 24 to 48 hours. If your dog is otherwise acting normal, still playful, eating, and drinking water, it's usually just a matter of waiting it out and keeping things bland for a day or two.

Can switching dog food cause diarrhea?

Yes, switching dog food too quickly is one of the most common (and most preventable) causes of loose stools in dogs. A dog's gut microbiome needs time to adjust to new proteins, fiber sources, and nutrient profiles. Dumping a brand-new food in the bowl all at once, even a better food, can cause temporary digestive upset because the bacteria in your dog's gut haven't had time to adapt.

This is why a gradual transition over 7 to 10 days is always recommended. Start by mixing about 25% new food with 75% of their current food, and slowly shift the ratio over the course of a week. We'll cover the exact transition schedule later in this article. And while you're adjusting meals, keep in mind that UC Davis School of Veterinary Medicine recommends treats make up no more than 10% of your dog's daily caloric intake, even healthy ones. During a food transition, keeping treat portions in check helps you isolate what's actually causing any changes in your dog's stool.

Can stress cause diarrhea in dogs?

Absolutely, just like in humans, stress hits dogs right in the gut. Moving to a new home, changes in routine, a new family member (two-legged or four-legged), thunderstorms, separation anxiety - all of these can trigger loose stools.

And it's not just anecdotal. A 2023 study published in Frontiers in Veterinary Science found that anxiety disorders in dogs hyperactivate the HPA axis (the body's central stress response system), flooding the body with cortisol. That excess cortisol disrupts the balance of bacteria in the gut and increases intestinal permeability, essentially making the gut wall "leakier" and less effective at its job. So when your dog gets diarrhea every time there's a thunderstorm or you leave them at a boarding facility, there's a concrete physiological reason for it.

Stress-related diarrhea often resolves once your dog adjusts, but chronic stress can lead to ongoing digestive issues that may need a vet's attention.

Could my dog have a food sensitivity or allergy?

If your dog's loose stools are a recurring pattern rather than a one-off event, food sensitivities could be the underlying issue. But it's worth understanding how common this actually is. According to a review published in Veterinary Quarterly, adverse food reactions affect up to 8% of the general dog population. That number jumps significantly in dogs that already have allergic conditions (research published in the Journal of the American Veterinary Medical Association estimates that 20 to 35% of dogs with atopic dermatitis also have adverse food reactions).

Here's the nuance most articles miss: food allergies account for roughly 10 to 15% of all allergic skin disorders in dogs, and only a subset of those dogs show gastrointestinal symptoms alongside the skin issues. So if your dog has chronic loose stools but no skin problems, food allergies might not actually be the cause, even though it's the first thing many pet parents suspect. An elimination diet supervised by your vet is the most reliable way to find out for sure.

When food is the trigger, common culprits include corn, wheat, soy, dairy, and certain proteins. Dogs with food sensitivities often show other signs too: itchy skin, ear infections, excessive licking, or gas that could clear a room.

The challenge is that many commercial dog foods and treats are loaded with these common allergens as cheap fillers. Corn, wheat, and soy are inexpensive ways to bulk up a product, but they offer little nutritional value to your dog and can wreak havoc on a sensitive digestive system.

Can the ingredients in my dog's food be causing loose stools?

They absolutely can, and this is where a lot of pet parents start connecting dots they hadn't considered before. Not all dog food is created equal, and many conventional kibbles and treats contain ingredients that are technically "food" but far from what you'd consider nutritious.

We're talking about rendered meat meals (which can come from a mix of animal parts, sometimes from questionable sources), artificial preservatives, synthetic colors, glycerin, and those filler grains we just mentioned. Your dog's digestive system has to work overtime to process these ingredients, and for many dogs, it's a losing battle. The result? Chronically soft stools, inconsistent poop quality, gas, and a gut that's constantly under stress.

Glycerin is a particularly sneaky one. It's widely used in dog treats to add moisture and sweetness, but it can cause digestive upset in many dogs. If you've noticed your pup's stools get worse after certain treats, check the label for glycerin. You might be surprised how common it is.

What about infections and parasites?

Giardia, roundworms, hookworms, coccidia, salmonella, and E. coli are all common culprits that can set up shop in your dog's gut and cause diarrhea. Puppies and dogs with weakened immune systems are especially vulnerable, but any dog can pick these up from contaminated water, soil, or contact with infected animals.

If loose stools come with other symptoms like vomiting, lethargy, blood in the stool, or loss of appetite, an infection or parasite could be at play, and a vet visit is in order.

Can medications cause loose stools?

Yes, particularly antibiotics, which are notorious for disrupting the gut microbiome. If your dog recently started a new medication and you're noticing digestive changes, talk to your vet. They may recommend a probiotic supplement or adjust the dosage.

When Should I Take My Dog to the Vet for Diarrhea?

You should see a vet if the diarrhea lasts more than 48 hours, contains blood, is accompanied by vomiting or lethargy, or if your dog is refusing to eat or showing signs of dehydration. Most cases of loose stools resolve on their own or with minor dietary adjustments, but there are times when they signal something more serious.

Remember, the WSAVA's 2025 clinical guidelines confirm that the vast majority of acute diarrhea cases are mild and manageable with supportive care. Those same guidelines also found, with high certainty, that antibiotics are not needed for mild to moderate cases, so if your dog has a day or two of loose stools but is otherwise eating, drinking, and acting like themselves, your vet will likely recommend dietary management and monitoring rather than jumping straight to medication.

Head to your vet (or an emergency clinic) if you notice any of the following:

• Blood in the stool - whether it's bright red or dark and tarry, blood is always worth investigating
• Vomiting combined with diarrhea - this combination can lead to rapid dehydration, especially in small dogs and puppies
• Diarrhea lasting more than 48 hours - even if your dog seems fine otherwise, persistent diarrhea needs professional attention
• Lethargy or refusal to eat - a dog that won't eat and has diarrhea is telling you something is genuinely wrong
• Signs of dehydration - dry gums, sunken eyes, loss of skin elasticity
• Your dog is very young, very old, or has existing health conditions - these dogs have less margin for error when it comes to fluid loss
• Suspected ingestion of something toxic - if you think your dog ate something poisonous, don't wait for symptoms to worsen

When in doubt, call your vet. A quick phone consultation can help you determine whether you're dealing with a wait-and-see situation or something that needs immediate attention.

What Should I Feed a Dog With Diarrhea?

For mild cases, start with a brief fasting period (12 to 24 hours for adult dogs, not puppies) followed by small, frequent meals of bland food. Plain boiled chicken breast with white rice is the classic go-to. Keep portions small and feed 3 to 4 times throughout the day rather than one or two large meals.

Once your dog's stools start firming up, gradually reintroduce their regular food over 2 to 3 days.

What if loose stools keep coming back?

If soft, inconsistent stools are a pattern for your pup, the real question isn't just "how do I fix this right now," it's "what am I feeding my dog that might be causing this in the first place?"

This is the part where we encourage you to flip over the bag of whatever you're currently feeding your pup and really look at the ingredient list. If you see things like corn gluten meal, meat by-products, artificial colors (Red 40, Yellow 5), BHA, BHT, propylene glycol, or a long list of ingredients you can't pronounce, your dog's gut might be fighting an uphill battle every single day.

Dogs thrive on simple, real food - actual meat, recognizable ingredients, minimal processing. Their digestive systems evolved to handle whole proteins and natural nutrients, not heavily processed fillers and synthetic additives.

How Does Better Nutrition Support Long-Term Digestive Health?

Higher-quality nutrition supports your dog's digestion by reducing the number of irritants and hard-to-process ingredients their gut has to deal with daily. Switching to better food won't cure every case of diarrhea (parasites don't care how premium your dog's diet is), but for the millions of dogs dealing with chronically soft stools and sensitive stomachs, what they eat every day is almost always a major factor.

And you're not alone in thinking this way. According to a 2025 Ipsos survey of American pet owners, 91% of pet owners ages 18 to 34 actively seek out pet foods with specific health benefits like gut health and digestive support. If you're reading this article because you want better for your dog's digestion, you're part of a massive shift in how people think about what goes in their pet's bowl.

Here's what to look for if your dog's digestive health is a priority:

Why do limited ingredients in dog food matter?

Fewer ingredients mean fewer potential triggers for digestive upset. When a product has a short ingredient list of things you can actually identify, like real chicken, vinegar, and rosemary extract, there's far less chance of something in there irritating your dog's system. Full Moon's Jerky Treats are made with five ingredients or less, and their Organic Jerky line is Oregon Tilth or USDA Organic Certified for pet parents who want to go even cleaner.

What does "human grade" actually mean for my dog's digestion?

"Human grade" isn't just a marketing buzzword, it's a federally defined standard. According to AAFCO's official guidelines, every ingredient in a human-grade pet food must be stored, handled, processed, and transported in compliance with 21 CFR Part 117, the same federal regulations that govern human food manufacturing. The product must be made in a USDA-inspected facility that's also registered with the FDA as both a food and feed establishment. And AAFCO's FAQ on human grade claims makes clear that no co-mingling of human-grade and non-human-grade ingredients is permitted prior to final packaging.

Why does this matter for your dog's digestion? Because feed-grade pet food (which is what most commercial dog food is) can legally contain rendered meats, 4D animals (dead, dying, diseased, disabled), and ingredients that would never pass inspection for human consumption. Your dog's gut knows the difference, even if the label makes it hard to tell.

Every Full Moon product, from treats to complete meals, is made with 100% human-grade ingredients in USDA-inspected kitchens. It's the same standard they'd use if they were cooking for people.

Why should I avoid glycerin in dog treats?

Glycerin is used in countless dog treats as a moistening agent and sweetener, but it can cause stomach upset, gas, and loose stools in many dogs, especially with regular use. Full Moon's entire product line is glycerin-free. Their Natural Essentials collection uses cassava root instead to achieve that soft, chewy texture dogs love. Cassava root is a natural, grain-free starch that's gentle on the stomach and easy to digest.

Does the way dog food is made affect digestion?

Yes, how dog food is processed matters just as much as what goes into it. Most conventional kibble is manufactured using high-heat thermal extrusion, which is efficient for mass production but strips away a significant amount of nutritional value and can create compounds that are harder for dogs to digest.

We, at Full Moon take, a different approach. Our treats are slow-cooked under low heat in small batches, preserving more natural nutrients and flavor. Our Pure Protein Air-Dried dog food takes this further, made with 90% real meat and air-dried to lock in nutrients and amino acids without artificial preservatives. It's shelf-stable, easy to serve, and formulated to meet AAFCO standards for complete and balanced adult nutrition.

For pup parents who want to go the fresh food route, Freshly Crafted frozen dog food is flash-frozen to preserve peak nutrition with zero preservatives. With 97% of its protein coming from USDA-certified animal meat and liver, it delivers the kind of nutrition that supports a healthy gut from the inside out.

And if better nutrition feels like a bigger investment, know that you're not the only one making that choice. A 2025 Ipsos survey found that 59% of pet owners are more likely to pay a premium for their pet's food than for their own. When your dog's gut health is on the line, most pet parents have already decided it's worth it.

How to Switch Your Dog's Food Without Making Things Worse

Even the highest-quality food will cause digestive upset if you switch too fast. A gradual transition gives your dog's gut bacteria time to adapt to the new nutrient profile. Follow this general timeline:

• Days 1-2: 25% new food, 75% current food
• Days 3-4: 50/50 mix
• Days 5-6: 75% new food, 25% current food
• Day 7: Full transition to the new food

Watch your dog's stools throughout the process. Some softening during the first few days is normal. If things get significantly worse, slow down and extend each phase by a day or two. Every dog's gut adjusts at its own pace.

This same gradual approach applies to treats. If your dog has been eating treats loaded with fillers and glycerin, switching to something cleaner won't upset their stomach as long as you ease in. Organic Chicken Training Treats at less than 3 calories per treat are a great starting point, with simple organic ingredients in a small, easy-to-digest bite.

The Bottom Line

Loose stools happen. Dogs eat things they shouldn't, get stressed, pick up bugs - it's part of life with a four-legged family member. But if soft, mushy, or inconsistent stools are a regular occurrence for your pup, it's worth taking a hard look at what you're putting in their bowl every day.

The ingredients in your dog's food and treats are the foundation of their digestive health. Simple, recognizable, human-grade ingredients that are minimally processed and free from common irritants like glycerin, corn, wheat, and soy give your dog's gut the best possible chance to do its job well.

Your dog can't read ingredient labels, but you can. And making that one change might be the thing that finally gets their digestion on track for good.