Almost every owner who has used boarding kennels knows the routine. The dog goes in with normal stools and comes out three days later producing something the staff describe, apologetically, as unsettled. It happens often enough that most kennels mention it at drop-off, and often enough that owners assume the dog was fed something it should not have been. Usually it was not.
What has actually happened is that six or seven independent things changed at once, each of which alone would be enough to disturb a dog’s digestion. Knowing which of those changes are avoidable, and which are hiding an infection rather than a stress response, is what separates an owner who manages the fortnight well from one who spends it worrying.
Six changes arriving on the same day
The water is different. Mineral content in UK tap water varies enormously, hard across the south and east, soft through much of Wales and Scotland, and taste varies with it. The evidence that water change alone causes diarrhoea in dogs is thin, and worth being honest about. The more reliable effect is that some dogs drink noticeably less of unfamiliar water for a day or two.
The food is different, often abruptly. The routine is different: new feeding times, new walk times, no sofa, no garden door. Sleep is different and usually much worse, because kennel blocks are noisy and dogs that would normally sleep twelve to fourteen hours across a day and night get considerably less. The bacterial environment is different. And underneath all of it, the dog is producing stress hormones at levels it does not produce at home.
Anything intended to support digestive stability is more useful as an established part of a routine than as an emergency measure, which is why Probiotic Dog Chews are more sensibly introduced a fortnight before a boarding date than handed over at reception on the morning of drop-off. A complementary feed a dog has already been taking for two weeks is one of the few things about that week which is not new.
What stress hormones do to a dog’s bowel
Stress-related diarrhoea is not vague or psychosomatic. The mechanism is well described across mammals, and it is physical.
Corticotropin-releasing factor, released in response to a stressor, acts on receptors in the gut wall as well as in the brain. The effect is to slow gastric emptying while speeding movement through the colon. Food sits longer in the stomach and passes faster through the large intestine, which is precisely the combination that produces urgency and loose stools. Adrenaline meanwhile redirects blood flow away from the digestive tract towards skeletal muscle, which is useful for running away and unhelpful for absorbing water.
A third effect is less widely known. Acute stress increases intestinal permeability: the tight junctions between the cells lining the gut loosen, allowing larger molecules and bacterial products across the barrier. That contributes to inflammation in the bowel lining, and is part of why stress colitis produces mucus and sometimes blood rather than simply watery stool. Studies of dogs entering shelters have also found measurable shifts in gut microbiota within days of arrival.
Kennel diarrhoea: what it looks like and why it usually passes
The typical picture is large-bowel diarrhoea beginning between twenty-four and seventy-two hours after arrival. Large-bowel means frequent small volumes rather than large puddles, urgency, straining at the end, visible mucus, and sometimes streaks of fresh blood. Fresh blood in this pattern usually indicates an irritated colon rather than something dangerous, though it is worth mentioning to a vet if it persists.
The distinction that matters is between this and small-bowel diarrhoea, which produces large volumes, weight loss and often vomiting, and is more likely to reflect infection. A dog with large-bowel signs that is otherwise bright, eating and drinking is usually dealing with a stress response that settles within two to five days.
Two things make it worse than it needs to be. The first is intermittent eating: a stressed dog refuses breakfast, is offered extra later, then eats a full portion hungrily, and the irregular loading itself disturbs the bowel. The second is well-meaning intervention, with staff offering chicken and rice because the dog is off its own food. Each addition is another variable.
Why sending the dog’s own food matters more than owners think
Abrupt diet change is one of the best-established causes of loose stools in dogs, and it is the single most avoidable factor in the whole scenario. A kennel that offers a house food does so as a convenience, not a recommendation. Switching a dog onto an unfamiliar diet on the same day it loses its home, its people and its routine stacks two significant stressors that could easily have been one.
Sending food is only half the job. Sending it measured is the other half. Portioning the whole stay into labelled per-meal bags removes guesswork, prevents generous scooping, and makes it obvious at collection how much the dog actually ate. A written feeding sheet giving quantities in grams, feeding times and a short description of what normal looks like for that dog is worth more than owners assume, because kennel staff have no baseline to compare against.
What else is worth packing, and what is not
Unwashed bedding carries familiar scent, and while the evidence for scent reducing measurable stress markers in dogs is modest rather than compelling, it costs nothing. Medication should go in its original packaging with written instructions, alongside the practice’s number.
What not to send matters equally. A new chew or a first-time dental stick chosen as a comfort item introduces exactly the dietary novelty the rest of the plan is designed to avoid. Anything the dog might destroy and swallow while anxious is better left at home.
The causes that are not stress at all
Group housing carries genuine infectious risk, and attributing every post-kennel upset to nerves means some gets missed.
Giardia is the most common. It is a protozoal parasite spread by cysts in faeces, which survive well in damp conditions and contaminate shared water bowls, runs and grass. The incubation period runs roughly one to two weeks, so signs frequently appear after the dog is home and the connection is never made. The classic presentation is pale, greasy, foul-smelling stools that come and go over weeks rather than settling. Diagnosis needs faecal testing, sometimes across several samples, and treatment is prescription-only.
Campylobacter is common in young dogs and in group housing, and is one reason hand hygiene after handling faeces is not excessive caution, since it transmits to people. Salmonella is less common but occurs. Both can produce diarrhoea with blood and mucus resembling stress colitis.
Canine infectious respiratory disease, still widely called kennel cough, is not a digestive illness but it changes eating. The incubation period is usually three to ten days, so the cough often starts once the dog is home. A dog with an inflamed throat eats less and may retch up white foam, which owners regularly report as vomiting. Vaccination reduces severity rather than guaranteeing prevention.
Preparing in the weeks before, not the day before
Most of what helps has to happen well in advance, which is the part owners most often miss. A trial stay is the highest-value preparation available: one day visit, or a single overnight a month or two before the real booking, means the dog’s first experience of the kennel is not also a fortnight long.
Vaccination timing needs checking against the kennel’s policy and the specific product used, and that is a conversation for the practice several weeks ahead rather than the final week. The same applies to parasite treatment. If the dog will be crated, practising that at home makes the kennel run less novel. If feeding times differ substantially from home, shifting the schedule gradually across a fortnight removes one more change from drop-off day. Taking a few litres of water from home for the first day or two costs nothing.
Car travel and motion sickness
Travel sickness is a separate problem with a separate mechanism, and it is worth understanding because owners routinely assume it is permanent when it usually is not.
Motion sickness arises from conflict between what the vestibular system in the inner ear reports and what the eyes report. In puppies the vestibular apparatus and its connections in the brain are still maturing, which is why travel sickness is far more common early on and why a large proportion of dogs simply grow out of it, often by around a year old. A dog that vomited in the car at four months is not necessarily a dog that will vomit at four years.
The complication is learned anticipation. A dog whose only car journeys end at the vet, the groomer or the kennel develops nausea before the engine starts, and that response persists long after the developmental cause has resolved. Breaking it requires short journeys that end somewhere good, repeated often enough to change the association.
The early signs are behavioural rather than digestive: drooling, repeated lip licking, excessive yawning, whining and an inability to settle. Practical measures include a secure forward-facing crate or harness so the dog is not fighting the corners, a cool interior with windows lowered slightly, and avoiding a large meal beforehand without travelling on a completely empty stomach. Where a dog is badly affected there is a licensed prescription medication for motion sickness in dogs, which is a conversation for a vet.
When to speak to your vet
Mild, short-lived loose stools in a bright dog after a stay are expected. These are not:
- Diarrhoea continuing beyond three to five days after coming home
- Large-volume watery diarrhoea, or diarrhoea with repeated vomiting
- More than a trace of fresh blood, or stools that are black and tarry
- Pale, greasy, foul-smelling stools that come and go over weeks
- Refusal of food beyond one or two missed meals, particularly in a small or young dog
- Lethargy, collapse, or a dog that will not get up
- Tacky gums, sunken eyes or skin slow to spring back, all suggesting dehydration
- A cough, nasal discharge or retching, especially alongside reduced appetite
The first week back
Expect a resettling period of two to five days, and resist the urge to fill it with interventions. Keep the food exactly as it was before the stay. Do not introduce a new diet, a new supplement and a new chew in the same week; if things go wrong there is then no way to tell which caused it.
Expect the dog to sleep a great deal. Kennelled dogs accumulate a real sleep deficit, and one that spends the first two days flat out is recovering rather than unwell. Some dogs are clingy for a few days and others withdraw; both are normal and both pass.
Weigh the dog at collection and compare it with the pre-stay weight, because a fortnight of reduced intake shows on the scales before it shows to the eye. If loose stools are still present a week after coming home, the sensible next step is faecal testing rather than another round of bland food, since a parasite picked up in group housing will not resolve on chicken and rice. Then note what worked for next time, because that record makes the next booking considerably easier to plan.
