When your dog starts eating grass and ends up with loose stool, it can be confusing and worrying.
One may assume it’s just a quirky habit, but it can actually signal something going on in your dog’s stomach or diet.
We outline the common reasons for dogs eating grass and having loose stool, what you can do at home, and when to seek veterinary help.
Dog Loose Stool Eating Grass: Why It Happens
Dogs may have loose stool after eating grass due to digestive irritation, diet imbalance, or underlying gastrointestinal problems.
While some dogs eat grass simply because they enjoy the texture or taste, others do it to soothe an upset stomach. The fibrous blades can stimulate vomiting or bowel movement, which may result in soft or watery stools.
Parasites, food sensitivities, stress, or even boredom can also contribute to the combination of grass eating and diarrhea.
Common Causes of Dog Loose Stool Eating Grass
Digestive Upset or Mild Gastroenteritis
Eating grass often happens when a dog feels nauseous or uncomfortable. The rough texture of grass blades irritates the stomach lining slightly, which can induce vomiting or speed up digestion.
When the digestive system is already sensitive — perhaps from a change in food, spoiled treats, or overeating — grass eating can push it over the edge. The result? A bout of loose stool or mild diarrhea that clears within a day or two.
Dogs with gastroenteritis may also show signs like drooling, gurgling stomach sounds, or loss of appetite. If the loose stool persists beyond 48 hours, it can lead to dehydration, and that’s when veterinary help is needed.
Read more: Dog Soft Stool and Not Eating (What it means)
Dietary Imbalance or Fiber Deficiency
Some dogs eat grass instinctively to make up for missing nutrients or fiber in their diet. Fiber helps regulate bowel movements, and when it’s lacking, the digestive system can become irregular.
Low-fiber diets or sudden diet changes may cause stool to become loose, especially when grass acts as a natural roughage. While grass itself provides some fiber, it isn’t a balanced substitute — too much can actually worsen the problem by irritating the intestinal lining.
In this case, improving your dog’s diet with appropriate fiber sources, such as pumpkin or green beans, can help stabilize the stool and reduce the urge to graze.
Parasites or Intestinal Worms
If your dog frequently eats grass and has loose stool, intestinal parasites might be the hidden culprit. Worms like hookworms, roundworms, and giardia can cause stomach irritation, leading dogs to eat grass to relieve discomfort.
Loose stool caused by parasites often has a foul odor and may contain mucus or small visible worms. Your dog may also lose weight, lick the rear area more often, or seem generally unwell.
Regular deworming and fecal tests are essential to rule this out. Even indoor dogs can pick up parasites from contaminated soil, other animals, or unwashed paws after outdoor walks.
Food Sensitivities or Allergies
Dogs with food sensitivities often experience chronic loose stool and sometimes resort to eating grass to calm their stomachs. Certain proteins, grains, or artificial additives can inflame the intestinal lining, leading to diarrhea and discomfort.
When the digestive tract becomes irritated, your dog may instinctively turn to grass as a self-soothing mechanism — similar to how some dogs eat dirt or chew on plants.
Switching to a limited-ingredient or hypoallergenic diet may improve stool consistency and reduce grass-eating behavior over time. Always introduce new food gradually to prevent further digestive upset.
Stress, Anxiety, or Boredom
Grass eating isn’t always about digestion — sometimes it’s emotional. Dogs under stress or lacking stimulation may chew or eat grass as a coping habit. This behavior is similar to nail biting in humans — it’s repetitive, comforting, and can temporarily relieve anxiety.
When stress-induced grass eating is paired with loose stool, it’s often because anxiety itself affects gut motility. The gut-brain connection in dogs is powerful; adrenaline and cortisol can disrupt normal digestion, resulting in softer stools.
If your dog’s behavior changes alongside the loose stool — like pacing, whining, or clinginess — emotional stress could be playing a role.
Ingesting Pesticides or Chemicals on Grass
One often-overlooked reason for loose stool after eating grass is chemical exposure. Many lawns are treated with fertilizers, herbicides, or pesticides that can irritate your dog’s stomach and intestines.
If your dog eats grass that’s been recently sprayed, they might experience drooling, vomiting, or diarrhea within hours. Even minimal exposure can upset the gut microbiome and cause loose stool.
Always monitor where your dog grazes and try to redirect them away from treated lawns or unknown areas. Providing safe, untreated patches of grass can reduce the risk.
Read more: Dog Loose Stool with No Other Symptoms (What it means)
What to Do If Your Dog Has Loose Stool After Eating Grass
If your dog develops loose stool after eating grass but otherwise seems normal, it’s okay to monitor them for a short period at home.
Start by withholding food for 8–12 hours (while still providing water) to give the digestive system time to reset. Then reintroduce a bland diet of boiled chicken and rice for 1–2 days before returning to their regular food.
Keep them hydrated, as even mild diarrhea can cause fluid loss. You can offer electrolyte supplements made for pets if the weather is warm or the diarrhea persists more than a day.
Encourage your dog to rest and limit access to untreated grass while their stomach settles. If the grass eating continues, consider enriching their routine with more play, chew toys, or short training sessions to reduce boredom-related behavior.
If you recently changed their food or treats, switch back temporarily to see if symptoms improve. Gradual diet transitions are key to preventing further digestive upset.
When to Call or Visit Your Vet
Call your veterinarian if your dog’s loose stool lasts longer than 48 hours or if it’s accompanied by other symptoms like:
Vomiting or refusing food
Blood or mucus in stool
Signs of dehydration (dry gums, sunken eyes, lethargy)
Persistent grass eating or pica behavior
Weakness or trembling after diarrhea
These can indicate a more serious issue such as infection, poisoning, or organ dysfunction.
If your dog frequently eats grass and has recurring digestive issues, a fecal exam and blood test can rule out parasites, allergies, or pancreatic problems. Early diagnosis helps prevent chronic irritation or nutrient absorption issues.
Read more: Old Dog Loose Stool (Common Causes)
Key Takeaway
Eating grass followed by loose stool is often a sign that your dog’s stomach isn’t feeling its best — whether from mild irritation, diet imbalance, or stress.
Most cases resolve with rest, hydration, and a bland diet, but repeated episodes can point to parasites, allergies, or even toxic exposure.
By observing your dog’s eating habits and stool quality, you’ll quickly learn when it’s safe to wait and when it’s time to see the vet. Trust your instincts — and remember, occasional grass nibbling is natural, but frequent loose stool deserves attention.