16/04/2026
Did You Know?
Horses cannot breathe through their mouths. Which is hard for us mere humans to understand, as we can do both. We humans can breathe with our mouths and our noses.
But horses are what we call ‘obligate nasal breathers’. As in they are obliged to do it, only breathe with their noses. Obligate means there is no alternative, it’s not a preference for them, it’s not a choice. It’s a requirement.
And nasal refers to the nose. So when we say a horse is an obligate nasal breather, we are saying:
👉 They can only breathe through their nose (no option)
👉 Their anatomy physically prevents them from breathing through their mouth (i.e they just can’t do it)
This is not the same as us humans. Humans can breathe through both the nose and the mouth, we can choose. If your nose is blocked, you simply switch to mouth breathing. Horses cannot do that! The structure of the horse’s airway, particularly the position of the soft palate, means that airflow is 'directed exclusively through the nasal passages' (their nose). Air cannot be drawn in through the mouth in the way it can in humans.
It also means when a horse has ‘just a nosebleed’ (EIPH), it is not the same as us humans. If a horse is bleeding from their nose, it is the same as us coughing up blood, like heisenberg in breaking bad, all is not well...
So breathing, oxygen intake, and airflow during exercise are entirely dependent on what is happening at the nose. And this is where it becomes important, not just for Exercise-Induced Pulmonary Hemorrhage (EIPH), or “bleeding”, i.e. a 'nosebleed' that occurs when strenuous exercise causes lung capillaries to burst, leading to blood in the airways, sometimes appearing as a ‘nosebleed’ (epistaxis), BUT also because we apply equipment to horses that might stress their normal anatomy.
If we misunderstand something as simple as how a horse breathes, which we as humans do a lot, we risk misunderstanding everything that sits on top of it:
– how they perform (we need oxygen to perform)
– how they respond under pressure
– how comfortable they are in the work, if we can't breath how can we be comfortable in work?
– and how our equipment and handling may affect them, tack is a big issue here.
This isn’t just anatomy w***y terms for the sake of it, I promise. It directly links to welfare, training, and critically performance, if we are asking our horses to be athletes (which many of us are asking them to be). AND If airflow is restricted, compromised, or interfered with, the horse has no alternative route to compensate. Unlike us, they cannot simply “take a breath through the mouth.”
When we’re working with horses, especially choosing tack, we need to understand that breathing is entirely dependent on the nasal passages functioning freely. And that has implications for that horse. Because if the physiology is fixed (which it is), then everything we do around the horse has to work with that, not against it.
If this challenges something you’ve previously heard or believed, that’s okay. A lot of traditional explanations don’t always align with how the horse’s body actually works (we are getting there!) But when we understand the biology, we make better decisions for our horses. And better decisions lead to better welfare, better performance, and a clearer understanding of the horse in front of us.
References:
Fraser, A.F. (2010) The Behaviour and Welfare of the Horse. 2nd edn. Wallingford: CABI.
McGreevy, P. (2018) Equitation Science. Oxford: Wiley-Blackwell.
McGreevy, P. and McLean, A. (2010) Equitation Science. Oxford: Wiley-Blackwell.
Waran, N. (ed.) (2007) The Welfare of Horses. Dordrecht: Springer.
