What Is The Cause Of EOTRH In Horses?

(Original December 6th, 2017, Updated April 2023)

After the 2017 American Association of Equine Practitioners (AAEP) meeting featuring Dr. Paddy Dixon, the world’s leading expert on dentistry in horses, the cause of EOTRH in horses is still unknown.  But I have an idea that merits this blog.

Equine Odontoclastic Tooth Resorption and Hypercementosis (EOTRH) has always been known as the “ugly teeth of old horses.” However, there are several clues that I have put together, with the final clue given by Dr. Dixon at the meeting.

The first clue here is “old.”  This disease is not seen in young horses.

The second clue is that it primarily affects the incisor teeth, followed by the canines, and is rarely seen in the cheek teeth.  In other words, the disease appears mainly in the front of the mouth.

The third clue is that it is rarely seen in ponies and mini horses.

The fourth clue is that there has been no written discussion of this disease until recently. There has been no mention of it in the last 30 years and before this.

The fifth clue was given by Dr. Early at this meeting when he said the word “hypercementosis” may not be accurate. Instead, cemental hypertrophy may be more accurate because the teeth, reacting to the bone disease, enlarge to save the teeth.  In other words, the teeth are not the primary disease but a result of the underlying bone disease.

The final clue came from Dr. Dixon when he said he believed EOTRH is an autoimmune disease.  In other words, the horse is turning its immune system against itself, attacking the cells of the front of the mouth and killing them.

From the last two clues obtained from attending the AAEP meeting, I now have all the pieces to put forward my hypothesis of the cause of EOTRH in horses.  It is built upon my recent discovery of the world of plant lectins and the damage they cause to the gut wall lining in all animals.  Most of the research has been done in humans on lectin effects. The horse world of research is beginning to discover the gut microbiota, microbiome, and the consequences of anti-inflammatory drugs and antibiotics on these diverse bacteria.  But in humans, the studies have gone to the root of the problem by determining the cause of the microbiome (gut bacteria) dysfunction.

Steven Gundry, MD, is the leading expert on the effects of plant lectins on humans.  In summary, these plant proteins are defense mechanisms that discourage predators from eating them.  Please pick up a copy of his book, “The Plant Paradox,” to learn more about this.  

Gluten is an example of a lectin, but there are thousands more such as the more devastating Wheat Germ Agglutinin (WGA).  WGA is a lectin found in wheat covering (wheat bran, whole wheat, wheat middlings) that damages human bodies in 11 ways.  The primary effect of WGA is the mimicry of insulin, blocking insulin receptors on muscle cells leading to insulin resistance (IR), obesity and type 2 diabetes.  In 2012 a Nobel Prize was given for the discovery of cell hormone receptors being covered by lectins mimicking the hormones and disrupting their ability to do their jobs.

Receding gums, bulbous profile and inability to thoroughly clean the teeth.
Receding gums, bulbous profile, a ridged collar forming at the gum line and inability to thoroughly clean the teeth.

Should We Be Happy Feeding Byproducts To Our Horses?

Almost every commercial horse feed and treat has wheat middlings as its main ingredient, the stripped-away byproduct of wheat when the bran is removed to produce white flour.  Thousands of years ago, humans found that the whole wheat grain made us ill and soon learned that removing the outer layer of wheat was healthier.  Asians also found that removing the outer brown layer of rice was healthier.  Italians were introduced to tomatoes only 500 years ago and became ill from them until they removed the skin and seeds.  Lectins are concentrated in the skin of all plants and their seeds to make predators sick and thus make animals stop eating them.

The gut of all animals starts at our lips, where our skin meets our mucosa.  Lectins that are swallowed escape the effects of stomach acids and then, in the small and large intestines, physically penetrate the space between the tight junctions between the cells that line our gut (enterocytes).  It is only one cell layer thick, so this breach between the enterocyte cells creates an inflammatory response, like a splinter of wood penetrating our skin.  The result of this penetration of lectins can be seen under the microscope and is commonly called “leaking gut syndrome.”

In humans, Dr. Gundry has determined that lectins are behind all autoimmune diseases, including lupus, rheumatoid arthritis, psoriasis and Hashimoto’s Thyroiditis, among others.  He has treated over 10,000 patients with dozens of conditions recording inflammatory blood markers and has resolved these diseases by removing the causative agents.  In other words, his approach to disease is not to treat it but to remove the cause, followed by what Hippocrates noticed 2000 years ago, the body’s ability to heal itself once the cause is removed.

The smooth pink area at the end of this tooth is the reactive cementum it makes to save itself from rejection by the bone inflammation.
The smooth pink area at the end of this tooth is the reactive cementum it makes to save itself from rejection by bone inflammation.

What does this have to do with EOTRH in horses?

What if a lectin such as WGA found in the grains we feed horses, especially wheat middlings, damages the endothelium of the mouth and creates an autoimmune response in the underlying bone?  Before we conclude, let’s look at our defense mechanisms against lectins.

Sugar molecules attach to lectins and make them unavailable to cause gut damage.  These sugars are called mucopolysaccharides and are found in the saliva and the mucous lining of the entire gastrointestinal tract.  Therefore saliva is our first line of defense against plant lectins.  The second line of defense is stomach acid, and the third line is the specific bacteria digesting lectins such as gluten.  

If saliva is the first line of defense, what if the saliva is either diminished or restricted to the back of the mouth?  If this happens, could it be possible that in some horses that bite into their grain, the lectin damage to the gum endothelium becomes damaged?  A retrospective study needs to be done to determine if horses with EOTRH have also been fed grain.  Could this be why ponies and mini horses not fed grain don’t get this disease?  What about the horses fed grain that doesn’t get EOTRH?  Maybe these horses have better saliva distribution or better immune systems.  Maybe having fresh water during grain feeding is washing away the protective saliva (Tom Brady’s new book advocates NOT drinking water with meals for this reason).

Proving the theory that lectins from grain cause EOTRH needs data from good research.,  However, there needs to be a treatment for those with the disease now.  There is anecdotal evidence that applying a mushroom extract to the gums may alleviate or lessen the effects of EOTRH in horses.  This may be possible because it has been shown in humans that mushrooms have an anti-lectin impact.  In addition, my colleague in Sao Paulo, Brazil, told me he had seen improvement in horses whose incisors are brushed with honey.  While honey is bacteriostatic, the sugars binding to the lectins may also prevent further damage.

Two necrotic holes on the labial surface of 203 of this 24-year-old horse. The gums are starting to recede, pinpoint red spots are seen on the gums, and the prominent bull nose shape of the upper incisors indicates the onset of EOTRH.


There is mounting evidence from my clients taking the no grain challenge that horses who no longer eat any grains see improvement in behavior, weight management (thin horses become fat and fat horses become thin), sweating, conditioning and some skin and hoof problems.  I believe that grains cause inflammation in the horse’s gut and upset the natural microbiome (gut bacteria), which in turn causes illness and chronic protein deficiency.  I now further believe that horses may have other diseases with an autoimmune component directly caused by lectin damage and hormone mimicry by circulating lectins.  

In Parkinson’s research, it is becoming clear that lectins are disrupting the gut microbiome and that eliminating lectins and reestablishing the normal gut microbiome quiets and even reverses the disease.  Research in dementia, Alzheimer’s and other cognitive disorders in humans now find that lectins travel up the vagus nerve from the gut into the brain, creating inflammation.  The brain’s response to this starts with a “foggy brain, ” leading to more severe brain disease.  Is it also possible that lectins may be causing damage to the neurotransmitter dopamine or its receptors which is the root cause of Cushing’s disease in horses?  What about insulin resistance caused by WGA or metabolic syndrome?  These diseases are relatively new and could be associated with the modern husbandry practice of feeding grain.

One more exciting note.  At the AAEP meeting, there was much discussion around the discovery of dental caries (cavities) causing decay, leading to the fracturing of cheek teeth.  No one knows the cause of this, but again, it is a relatively recent phenomenon in horses, as there is little mention of cheek tooth fractures in older textbooks.  In 1932 a study was done on children who were developing a high number of cavities.  Researchers documented their observations, removed oatmeal from their diet (a standard back then), and added vitamin D and Cod liver oil.  The tooth decay went into remission and was eliminated within six months.  Could tooth decay also be associated with lectins?

There is evidence that all grains (wheat, corn, oats, barley, rye, quinoa, and others) are killing us.  Grains are less than 10,000 years old in our diets, 4000 years in civilizations (Egypt and the middle east), 2000 years in modern culture and maybe 50 years old in our horse’s diets.  Our gut microbes are overwhelmed, and the diseases and obesity that plague our horses and us are not rising because of better detection but are simply rising because of the survival changes we have made as a culture in beings that are well over 100,000 years old and many over 1 million years old.  It’s worth thinking about.

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  1. I am curious what would be the recommended to feed older horses when there is not enough grass. Where I live is in drought. My mare is having difficulty chewing hay so what is recommended as would prefer not to feed grain!

    1. It can be difficult to find a forage that horses with bad teeth can eat. Chopped hay, soaked hay cubes and soaked hay pellets are the standard. To add some weight please remember to add protein (such as soy bean meal) which will restore the muscle in the top line. To add some body fat I recommend shredded coconut meal (Coolstance) which is available in a lot of places throughout the world. This is a non-inflammatory fiber that can add some body fat especially in older horses as well as some additional good quality protein. a second choice is Renew Gold which has Coolstance in it but also has flax and rice bran which may be inflammatory in some horses.

  2. This is an interesting theory. However, I have to object to your statement that EOTRH is rarely seen with ponies. It is in fact very common with Icelandic horses (or ponies) in Europe. One reason for this may be that they tend to get older than many other breeds. As they are also very sensitive when it comes to proteins and sugar-rich diets, they are usually kept on a very sober diet. If they get additional fodder at all (especially in Iceland this is very rare, though more common on the European continent), this is usually low in protein and does not contain oats. I’m not sure whether that contradicts your theory but at least it is worth taking into consideration.

    1. Thanks Joris. As you noted, this is only a hypothesis to start a discussion. Icelandic ponies are not common here especially in FL but they do exist and I have heard that they can be easily fattened on grain and good grass so these are avoided.

      The question I think lies in the definition of “pony.” Here in the US it usually applies to Shetlands and to mini horses where I have not seen cases of EOTRH but many of them are fed grain. Also here we would not consider an Icelandic equine to be a “pony.” Therefore I think there may be a genetic component regardless of the animal’s size or the human’s terminology if Icelandics get EOTRH and are not fed grain.

      If Icelandic equines do have EOTRH and are not fed any grain then I would be interested in this. Remember that my hypothesis is that the lectins are at the root of this possible autoimmune disease of the incisive and mandibular bones. All plant seeds have lectins that can adversely affect the horse and human according to new research. Is there anything being fed to these Icelandics with EOTRH that is not natural to their historic diet? Obviously this would be the case if they have been exported off of their native land. Is there EOTRH in Icelandic equines in Iceland? I believe this is where research needs to focus on – the diets associated with this disease because in humans, autoimmune diseases can be reversed or eliminated when lectins are removed from the diet.

      Thanks for your thoughts and hopefully someone with good research sense can look into this more effectively.

  3. Doc T,

    Yesterday, my local dental vet provided the annual float for horses. His practice is founded in dental work only and he has approximately a decade of experience as a vet. It was found that my 18-year old Warmblood Gelding had two concerns. First, an upper cheek molar, 110, was fractured. The vet extracted two pieces of the crown; leaving the center piece. Additionally, he took x-rays and determined that the root of 110 appeared normal but the root and associated structures (not crown) of 109 seemed impacted by the fracture; infected was the words he used.

    Secondly, the vet informed me that my horse has EOTRH on upper and lower incisors plus all four canine teeth. The x-rays do present hyper-cement on the roots. He has a tiny bit of tarter and evidence of recessed gums; lastly, 201, is bulbous compared to the other upper incisors. His immediate recommendation is to extract all upper/lower incisors and canines in addition to 109 and 110. The vet did a very good job explaining the x-rays and the disease and its progression. I find it interesting that this NEW disease has recently come about even though we all know that aged horses eventually experience dental concerns at the end of their lives.

    I have concerns regarding this recommendation. In the past, I had a late-teen gelding with fractured cheek molar and that vet extracted the broken crown pieces. The horse was euthanized at age 24 due to cancer localized in spleen. I have read your comments and know that your response is to extract pieces and allow nature to take its course without full extraction of tooth. I also read that dental x-rays are not necessary accurate given the condition in which they are taken and thus the quality of the images presented by the method. So for this experience and this horse, it was a win. The issue of ulceration and decay due to food impacts was removed and he lived to a natural death with all his teeth minus the crown. I am inclined to do so for my current horse.

    Now for the EOTRH concern, I have done a tiny bit of research on the Internet. It seems that my horse’s condition and its current progression is minor compared to what I have seen on the Internet. Last Spring, this same vet completed the same full extraction procedure on a similar-aged Thoroughbred gelding as he is recommending for my horse’s EOTRH condition. Within six months this horse died of an apparent ‘heart attack’. It’s owner was riding it in a fenced arena. Some neighbors cattle got loose and strolled up the drive which is adjacent to the arena. The horse had grave concerns. It’s owner dismounted and took the horse to the barn and removed its tack and returned her horse to its stall. The horse immediately collapsed and died. The attending vet diagnosed the collapse as heart attack. Thus my great reservation of going down the same path!

    We all know that teeth health is related to heart health. This horse was healthy prior to the extraction and recovered very quickly with only two follow-up visit of the dental vet. The horse went on to eat a normal diet. But then dies of heart attack! The horse was fit and ridden several times a week by an elderly lady who has riding skills so it is not like the horse was unfit or under-exercised. It should have sustain it ‘scare’ from the unusual event of the cattle losing up to the fence of the arena.

    My vet yesterday indicated the horse has pain. Initially I agreed as I have been having some minor bridling problems particularly when I ride with a curb/snaffle combo. But the horse also has an ulcerated cheek due to the fracture….He eats normally by taking his hay across the incisors. He has quid but now I know why due to the fracture. The fracture is slightly infected due to food impaction. Reading your posts, it is my understanding that horses do NOT have pain such as humans regarding tooth disease/health.

    I guess why I am writing this long story, is to find out if you are aware of horses dying as I presented above. I rather take a wait-and-see approach and up my annual float to a bi-annual dental exam and float. This dental vet is very conservative with a typical float. He does use power tools but takes only what needs to be done and not put in ‘bit seats’ due to the damage it creates with the pre-molars’ health. I have used two other people who will take 2 hours to float a normal horse whereas this vet does it in 15 minutes. So, I find him conservative but this recommendation is NOT conservative in my opinion.

    Your thoughts?

    Thank you for your thoughts, Lynne

    1. Thank you for finding and reading my blogs.

      In humans there is a relationship between Staph bacteria in the mouth, oral procedures / surgery and vegetative endocarditis and / or pericarditis. It has not been reported in horses to my knowledge.

      Here are some links for you to explore regarding EOTRH:

      I cannot advise on a horse I have not seen. I do approach dentistry in horses conservatively extracting teeth only when it is a last resort to resolve an issue that threatens the health of the horse such as an inability to chew. You need to have a frank discussion with your vet to weigh the advantages and disadvantages of extracting all the mentioned teeth including the complications that may occur such as the tongue forever hanging out of the mouth.

      Please return here and post your decisions and outcomes. Doc T

      PS – Is your horse fed grain? How much and for how long?

      1. Hi Doc T., I had frank discussion with the vet about delaying the extraction of all incisors and canine teeth.

        With available research on Internet, it is my opinion that my horse is presenting a MODERATE case of EORTH. At last year’s dental exam, there was no indication of the condition nor mention of it on the Exam report.

        I requested of the vet who specializes in dental work only and who has been in the DVM field for a decade with a recent specialization to dental work in the last three years that we go to a bi-annual exam and float while retaining all teeth and if the condition progresses to the point where the horse is in pain then remove those teeth most impacted at that time. His response was if I do not extract all the teeth now, within the next two-weeks, then I will not provide future services to your horses. His reasoning is that he is only providing partial services and thus he is not going to provide any service. I was offended by his response but can appreciate it even if I don’t agree with it.

        This vet was adamant that the horse is in pain. That is not the case, if you ask me he wanted to do the extraction immediately so that the horse could not recover from the float and thus indicate no pain with his incisors. Initially, my horse did present pain indicating head shyness when my hands approached his mouth. Since then, my horse is eating normally, readily accepts bridling and performs under saddle with no indication of mouth pain nor head shyness. He scraps his incisors against the stall wall (an old habit) and opens the sliding stall door with his nose (again an old habit). He bits down on things like the pitchfork and my jacket. He is presenting all of his typical behaviors prior to Feb 2018 exam.

        So, what I have done it switch him completely to an all-forage diet with the hopes of restoring his gut bacteria snd thus slowing the progression of his EORTH. I bought the Plant Paradox after reading your article and its reference to Dr. Gundry’s work. I know what happened….commercial feeds and oils. In the future, I will go to my regular vet for floating. The level of service will not be the same but for now given my situation, I will have to be satisfied with the services provided by my regular vet. I know the horse is not going to die of EORTH. My intent is for him to die with all this teeth intact.

        Thank you for your time and assistance. I love your articles. Keep up the good work.


        1. Thanks Lynne for your common sense and courage of being your horse’s advocate.

          I think we could all benefit from your observations over the next year (maybe every 3 months). Include clear photos and even a clear video of the horse using the incisors indicating any pain (or no pain). Following this course of no feed other than pasture and hay would be very interesting. No other foods should be given that he wouldn’t find in his real world with the exception of supplemental protein. I see that you have read the blog on protein too.

          1. Hi Doc T, I will post photos and radiographs that were taken in Feb 2019 and then give up dates periodically. Thanks for your support. Lynne

        2. Hi Lynn, I would like to know if the changes in your horse’s feed has slowed the progression. My gelding was recently diagnosed and I would also like to save his teeth.

          1. We all would like to know the results. In addition if there is anyone reading this with a horse having EOTRH and has NEVER been fed grain, I would like to hear it.

            A few of my clients have tried Equident (shredded mushrooms) and have seen diminished inflammation in the gums. They have also stopped feeding grain. Anyone have a spare million dollars to fund an experiment??

  4. I wonder that if this is indeed autoimmune in nature, would removing the trigger allow the condition to heal itself or only prevent further damage? Or might that also be contingent upon how long the disease has been going on?

    1. In Dr Gundry’s book, he has been able to reverse “all autoimmune diseases” (his quote). If this is the case, I would expect at least that the condition shouldn’t worsen and if in the non-clinical stages, start to resolve. In 1932 children removed from their daily breakfast of oatmeal either arrested development of carries (cavities) or resolved them. This observation has me wondering about lectins as a cause of central necrosis and cheek tooth fractures.

      If you win the lottery, please finance this research! Thanks in advance Tina! Doc T

  5. I am not a vet, but a holistic hoof care professional. Many hoof care issues are a symptom of imbalances in the body stemming from the diet. I personally ditched grains after reading “Wheat Belly”, by Dr William Davis with good results 3 years ago, but still struggled with nagging joint aches. After Reading Dr Gundry’s book, Plant Paradox and removing the lectins, those nagging issues have disappeared. I started to think about the implications of lectins in the horses diet, and came across this great post. Dr Gundry’s term “holobiome” really encompassed a much broader sense of the biome starting with what he called the “dust cloud” that surrounds us, using the Peanuts character, Pig Pen as an example. Kind of like the atmosphere surrounding our body. It’s pretty humbling to discover that 90% of the cells in and on our bodies are non-human! I have gained a whole new respect for it.

    Teeth and facial balance are the first parts of every horse I look at. Everything else follows from there so this post was again very interesting in that respect as well.
    I also feel we need to include that the grains used in horse feed beyond lectins are generally GMO, and even if they are not, they are often sprayed with Round Up to desiccate crops for a greater yield. Dr Zack Bush demonstrated how the tight junctions are opened in the gut in the presence of glyphosate, the active ingredient in Round Up. We also need to ask about the use of paste wormers which are given by mouth- Do they disrupt the mouth biome? If so, how, and can it fully recover if it is done on a regular basis? Should we be going after the bad guys, or as Dr Gundry puts it, support the good guys and the bad ones leave? He goes beyond food in his book when he talks about drugs, antibiotics, personal care products and his list of Trojan Horses. I too highly recommend the book. It sure opens up a different way of looking at homeostasis. Thanks so much for posting this. I look forward to reading more.

    1. Thanks for this. Hang on because I will be discussing GMO, Roundup, all medications and finally, how do we feed our horses now.

  6. Holy cow! I’ve never seen a horse’s teeth like that! I’m a trainer, not a vet, but I’m seeing possibly a calcium deficiency? I’d be interested in the blood values of poor horse! I also suspect, that condition didn’t happen overnight.

    1. Blood calcium is maintained in all mammals at a specific level so the only way to determine a Ca deficiency is to look for bone loss (osteopenia and osteoporosis). EOTRH is seen only in older horses and my hypothesis is that it is an autoimmune disease of the incisive, mandibular and maxillary bones caused by plant lectins in grain. As with all hypotheses, it needs to be further looked into and proven which I am unable to do now.

      1. Yes, you are right. Blood calcium levels would still be normal. Could the grain be too high in phosphorus? Further research is definitely required! I have in my possession, some very old veterinary books, one I have is over 100 yrs. old. And they too warn against too much grain in a horse’s diet! Pity, no one seems to read much anymore in this country.

        1. When phosphorus becomes equal or exceeds the calcium levels then calcium will be drawn from the bones leading to osteoporosis. This is seen when horses are fed excessive grain especially wheat bran. This is why all grains have dicalcium phosphate added to them.

          I too have some century old vet and husbandry books. Coupled with today’s research on grain lectins, there is now absolutely no reason to feed a horse (of us for that matter) grains.

  7. If grain was the cause of the disease wouldn’t it affect all the teeth as opposed to just incisors? It seems a lot of horses scoop grain with their lips and then chew with the molars. Either way this would be an interesting research.

    1. yes – very interesting. I think saliva distribution is key as the mucopolysaccharides bind to lectins making them ineffective. Another thought is that if the cheek teeth are sharp restricting tongue movement then the incisors may not either being cleaned or getting the saliva.