Ketoacidosis/Ketone stench on a horse WTF

As I was grooming a horse the other day, I thought I smelled something, but couldn’t pinpoint, it was a quick groom before riding. After riding, damn it, the smell is on me. Blech. Except it wasn’t. WTF? It had already lodged itself into my sinuses though so every time I bent down or moved my head in a specific way, there it was. Ugh.

I used to work with dairy cattle so I am very familiar with the smell of acidosis and I’m one of the lucky, lucky people who can smell it a day before it shows up on a dipstick as something of concern, so I am definitely very familiar with the awful stench that was stuck in my nose.

I finally traced the origin of the stink to the horse’s belly. Again, WTF? Horse is young and healthy and neither her breath nor her nether regions (nor her somewhat peed on tail flap of her blanket) smelled like acidosis. Ok, so it’s pretty probably not actually emanating from within her.

The best I can figure is maybe horse had a little lie down outside in some hay that was contaminated by some other horse’s pee. Horse IS out with a couple of antiques, but still, ketosis in horses isn’t really that much of a thing, right? Does anyone know of a horse who has suffered from ketosis?

Next question, do I approach BO to tell them one of their or another boarder’s horse may be sick because I smelled something a lot of other people can’t smell on a horse that isn’t sick and probably isn’t something that would normally be smelled on a horse at all?

Last question, is there anything that mimics that horrible stench that I don’t know about - a more plausible reason for smelling it?

TIA to anyone who has got this far :slight_smile:


Well, I definitely don’t know. But I find this fascinating.

It did prompt me to google around for what ketosis smells like to see if it might match up with other smells I’m familiar with (thrush, abscess, sheath due for a cleaning), which led me to all kinds of descriptions of human keto urine smell. Fruity, acetone, and popcorn all turned up. :face_with_raised_eyebrow: I don’t think I would describe any of my other familiar scents in that way, unless the popcorn smell is of the very… biological? variety.

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I have not heard of ketosis in horses but I understand what smell you are referring to. I’m not sure what exact biological cause of that smell would be in a horse.

Any time my nose has told me something and I’ve ignored it I’ve regretted it. I picked up a ditch dog that smelled “off”. It wasn’t a consistent smell, in passing I’d notice a scent like how a hoof abscess smelled. I didn’t know the dog well so gave him a day to settle before I started poking and prodding him. The next day I couldn’t ignore it and started looking all over the dog. I found a stick wedged/embedded in the roof of his mouth - it was awfully infected. It must have been in the roof of his mouth for a while because flesh had began to embed around it. Luckily, he was much better after some antibiotics from the vet.

Another time thought I smelled something similar around one of my horses. Poked and prodded at his mouth and teeth and couldn’t find anything. Dentist came out but didn’t see much either but did notice a slight ulcer that she felt was from a molar hook that wasn’t there in the last visit — this horse wasn’t even overdue either. A few weeks later an abscess burst though his cheek exactly where the ulcer was.

I’d say trust your nose. You don’t need to be specific, just say hey, when I’m around this horse I notice a smell that isn’t normal - has anyone else noticed anything? Beyond that there is not much you can do if it’s not your horse.

It could be something like her belly button or even udders — but again, without it being your horse I’m afraid there is not much you can do beyond try to talk to the BO or owner with your concerns.


Abscess was my first thought too! But I had no idea if that lines up with ketosis. Abscesses/infections do have a very specific smell. Maybe something in the belly/upper hind limb/armpit area (I’ve experienced this smell from a mean shoe boil that hid under the elbow) that’s hard to see? Could be worth a mention to the owner, but don’t be surprised if they find it odd that you’re reporting that their horse smells off. :laughing:

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Weird question - but was the horse grey?

I boarded a grey horse once and all I can say is that he smelled differently. I think I know what ketone smell is (like a diabetic person’s breath?) - I can’t quite remember if that was the same smell but I could never figure it out. It seemed to emanate from his skin.

And I feel like there was some conversation here on COTH about grey horses smelling differently.


The horse you described was a mare so my experience is likely not helpful. Years ago I hauled a gelding that “smelled wrong.” He belonged to a former friend who insisted he was “just fine,” despite some (odd to me) behaviors —kicking at whomever removed the butt bar (after one near miss, I made friend do it), aggression (ear pinning, tail wringing) toward other horses (I would not tie my boy on the same side), and general crabby-ness. But as I said, she loved him and thought he was just fine —until he bucked her off when she was riding solo --and kicked at her after she was on the ground.

She placed him in a center for handicapped riding (she must have lied her butt off) --after a 10 day trial, they found him “unsuitable” and he was given to a teenager who had him vetted --vet diagnosed ridgling (cryptorchid). Apparently it was an easy fix (some are not) and horse and teenager lived happily every after (I never saw horse again, but as he was already mid-teens, I wonder if the behaviors resolved).

But as I said, he “smelled wrong” from the get-go. I could always smell him in the trailer long after he was out.

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Ketosis smell in people is fruity and is often mistaken for an alcohol smell. Not sure about popcorn. And I don’t think, based on my experience, that it’s anything like an abscess, thrush, or infection.

Lots of diabetics in ketoacidosis are mistaken for drunks; LEOs will always describe the smell of alcohol as one of the reasons they concluded the person was drunk. (They also may appear uncoordinated and slur words.)

I think your theory of the horse lying in urine soaked hay is a good one.


Thanks all for your thoughts on this.

I did forget to include that this was a one-off occurrence. I have worked with the horse again a few times and there has been no smell. However, I caught a phantom whiff or two in the barn two days later after the horse’s buddies had been inside for a few hours in their stalls. I could not trace that smell as they had already returned outdoors and it was only a whiff, not even strong enough to latch onto my sinuses. Nothing at all since then.

For those wondering what the smell is like, I personally smell absolutely no hint of popcorn in it, for me it comes through as a very distinctly over-powering sour/sweet with an almost breath-catching quality to it - that feeling of stepping out into -30 weather and having your throat and lungs say, “WTF?” but not that drastic.

It is absolutely 100% nothing like infection or rotting flesh or smegma or stallion sweat
or unfit horse sweat odour.

The closest thing would be alcoholic breath with a heap of sourness added to it.


No, the horse is not grey and yes, I think the smell is the same. I’ve only ever smelled it strong enough to recognize on post-partum women as they go through metabolic nonsense, but I’m not much of a people person so I don’t get that close to many people lol.

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Ok I need to hear more about this because my grey also has a different smell!

I don’t know. I can’t remember if I read it, or if I was the one who asked it here. It was a LONG time ago, but it seemed like others agreed that their grey horses smelled different. But I only boarded the horse for the summer and he stunk. His sweat or his skin or something. And I had both mares and geldings, so it wasn’t a female/male thing.

It’s definitely when she sweats but she was suffering from malnutrition when I got her so I always thought it was a side effect from that. Now I’m so curious ahaha time to “research” lol

If the smell was coming from the belly area, I’d totally put my money on laying in pee!

Interesting that in people it has an alcohol-like smell. I always thought it was ammonia and due to utilizing protein for fuel. But is that just the sweat smell dying exercise and it’s different under rest conditions?

This reminds me of the house episode where the patient smelled like grapes. After quick googling this seems to be the bacteria from that episode causing the smell in that case

No idea what ketoacidosis smells like personally…

To me, a lot of greys have a smell that’s very faintly reminiscent of the lanolin in sheep’s wool. It’s kind of a gamey oily note that I haven’t noticed on darker colored horses. Not unpleasant, just noticeably different.
The ones I’m thinking of at my barn also have coats/manes that feel slightly greasy to me, so it might be related to that


Yes! This was exactly it. The slightly greasy feel of the mane is definitely memorable. So maybe it’s just the coat/skin type, and maybe more common in grey horses? I don’t know. It was noticeable from day 1 and I didn’t miss it when the horse left.

Just a note that ketosis and ketoacidosis are different things


We’re talking animals here, not the hair-splitting, diet-induced, maybe-arguably-healthy human state.

If we (and I include all the vets I’ve known in my life in dairy) are going to name a stinky sick metabolic cow’s disease, we are going to say, “She has ketosis” or “She is ketotic.” or “She has acetonemia” or “She is acetonemic.”

What is referred to as “ketosis” in humans may be referred to as “sub-clinical ketosis” in cattle. It ain’t good, it IS going to lead somewhere bad, it’s just a matter of how many directions it goes which can be a product of how long-term the sub-clinical disease state is present.


Golly gee, what??? I didn’t know this was a horse board. Thanks for the spankin’
But yeah, still two different words with different definitions. Also cattle aren’t horses if you want to go there


No. In veterinary medicine there is no hair-splitting. Ketosis is the disease. Dr. Joe Vet is not going to make a differentiation between ketosis and ketoacidosis even between mild (subclinical/barely registering) and much more severe, life-threatening disease.

I mean, I’m super open to you pointing out any veterinary material that says otherwise, but I don’t think you’ll find any. I’d like to be up to date if things have changed in the couple of years since I was dealing with ketosis on the regular!

Horses definitely aren’t cattle, and since ketosis is hardly known in horses, that’s why I posted here - to see if anyone else had ever experienced this bizarre thing that is not supposed to happen to horses.

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