11/06/2026
Did you know that your dog’s gut might be influencing their behaviour?
When we think about a reactive dog, we often focus on what’s happening outside the dog.
The barking.
The lunging.
The triggers.
But what if part of the picture is happening inside the dog?
Let’s talk about serotonin.
Serotonin is often called the “feel good” chemical, but that’s a bit of an oversimplification. It’s involved in mood, emotional stability, impulse control, sleep, appetite, learning and how we cope with stress.
Think of serotonin as one of the body’s natural “everything is okay” signals.
When serotonin levels are healthy, dogs are generally better able to cope with the ups and downs of life. They’re more likely to think before they react and recover more quickly from stressful events.
Here’s the really interesting bit…
Over 90% of the body’s serotonin is produced in the gut.
That’s right. Not the brain. The gut.
The gut contains trillions of bacteria, fungi and other microorganisms, collectively known as the gut microbiome. These tiny organisms help influence the production of serotonin and communicate with the brain via what’s known as the gut-brain axis.
You can think of the gut and brain as being in constant conversation.
If the gut isn’t healthy, that conversation can change.
Research in both humans and animals has found links between gut health and emotional wellbeing. We know that disturbances to the gut microbiome can influence mood, stress responses and behaviour.
Does that mean every reactive dog has gut problems?
No.
Reactivity is complex. Pain, genetics, fear, learning history, lack of life skills, hormones, sleep, stress and the environment can all play a role.
But if we’re trying to help a reactive dog, it makes sense to consider the whole dog, including what’s happening in their digestive system.
This is one of the reasons I always ask about diet, digestive issues, medication, food intolerances and overall health when discussing behaviour concerns.
Because behaviour doesn’t happen in isolation.
The brain and the body are part of the same team.
Have you ever noticed changes in your dog’s behaviour after a change in diet, illness, antibiotics or digestive upset?