Sarcoids in horses

Many years ago, long before I knew what a fibroblast was – or had ever heard of bovine papillomavirus – I knew one thing about sarcoids. They came back.

The name ‘sarcoid’ was originally given to the human condition in 1936 by a Dr. Jackson, a pathologist in South Africa. He used the name to describe the condition’s generally sarcomatous (tumourous) appearance. Prior to that, the condition was simply termed ‘wart’.

When it comes to our horses though, and no matter what products are out there, you’ll read everything from "Worked like a miracle," to "Didn’t help at all." One thing’s for certain though; they provide us humans with a level of hair-pulling frustration rarely seen with other equine conditions.

Personally I’ve not owned a horse with sarcoids, although my first pony passion when I was a child (jet-black Sec.C pocket-rocket Charlie at the local riding stables) had a horrid one on his left eyelid, year in and year out. It was the shape and size of an adult human thumb, and every year it was banded off, yet sure as eggs are eggs it would grow right back again the following year. Which makes perfect sense - the sarcoid itself may have died through having its blood supply banded off, but the virus was still in Charlie's body to regrow right back again.

Cut to five decades later, and my former neighbour had a very charming Appaloosa who, as long as I knew them (several years), had been afflicted with multiple sarcoids on his body, the worst being a horrible knarly growth, the size of a fist, literally surrounding his entire left eye socket. It was incredibly sore for him, with many open cracks, bleeding and weeping.

My neighbour spent every spare waking moment researching a fix for him, and trying just about every product on the planet, including expensive products from the US. Needless to say we shared lengthy chats on all things sarcoids.

Of course, over the years I’ve had my own thoughts and opinions on sarcoids - I’ve always believed that a struggling immune system was somehow at the heart of them, and as we all know, immunity is at the very core of, well, everything. If immunity is in some way compromised, ‘stuff’ happens, and we also now know that the immune system relies entirely on a healthy gut microbiome. So, with a healthy biome and a healthy, fully functioning immune system, in theory the body should be equipped and ready with a strong resistance to have a darned good go at fighting whatever's invaded the host body.

Nevertheless, without any concrete evidential proof of anything that actually worked for definite, whether natural or conventional, I’ve always been reluctant to promote any herbal support for the many enquiries we get for sarcoids, other than based around supporting immunity.

Sarcoids update - Sept'2026

* A quick heads-up here - the following are my condensed notes from my own research on sarcoids. Sources are below and equally it's all out there on the world-wide-web.

Back to Charlie pony, and back then we all thought that the sarcoid itself seemed to be the whole problem. It was the bit we could see, so naturally it was the bit everyone concentrated on.

But since doing a massive deep rabbit-hole dive recently, the subject of sarcoids has become far more interesting - the lump itself isn't really the beginning of the story at all. It's actually just the visible result of a much bigger conversation between a virus, the horse's genes, the local skin environment and an immune system that – for one reason or another – has not managed to keep those altered cells quiet.

That does not mean that “poor immunity causes sarcoids”. The biology is far more nuanced than that. But it does help us ask a better question - Why does one BPV-exposed horse develop sarcoids while another doesn't?

And once we ask that, our attention begins to widen from the lump itself to the horse underneath it.

Sarcoids in a nutshell

Back in 2017 - the last time I updated this page - I saw sarcoids principally as a dormant BPV infection waiting for a weakness in the horse’s immune defences, with gut health and immunity therefore the obvious places to focus. That thinking wasn’t entirely wrong… but it was missing a lot of the biological story that we now know today.

Sarcoids are the most commonly diagnosed skin tumours in horses. They are usually described as locally invasive but non-metastatic: in other words, they don't normally spread around the body in the way we associate with many cancers, say, but they can be persistent, they can infiltrate nearby tissue, and are renowned for being extremely difficult to manage.

They can appear as a flat, scaly patch; a wart-like area; a firm lump beneath apparently normal skin; an ulcerated, fleshy growth; or a mixture of several forms. Some remain quiet for years, while others change rapidly, particularly after trauma or inappropriate interference.

Here are the key pieces of the picture:

• Bovine papillomavirus – principally BPV-1 and BPV-2 – is central to sarcoid biology.
• BPV exposure alone does not explain why one horse develops a lesion and another does not.
• Genetic susceptibility, immune recognition and the local tissue environment all appear to influence what happens next.
• BPV DNA can be found in apparently normal skin, so its presence alone doesn't diagnose a sarcoid.
• There's no single treatment that's right for every sarcoid, and no supplement, medication or management practice has been proven to prevent all future lesions.

So, if you've found a suspicious lump, photograph it - and resist the urge to poke it, squeeze it, or attack it with the contents of the kitchen cupboard – and get your vet have a look. Sarcoids can be awkward enough without us issuing them a formal invitation to misbehave.

First things first – what actually is a sarcoid?

A sarcoid is a tumour involving fibroblasts, the cells that help produce and organise the connective tissue beneath the skin.

It’s thought that under the influence of BPV, these cells can be pushed away from their normal behaviour. They begin to proliferate abnormally, interact differently with the tissue around them, and become harder for the immune system to recognise and address.

And this last part matters. The virus is not simply sitting on the surface producing an ordinary wart. Sarcoid tissue creates its own little biological neighbourhood – often called the tumour microenvironment – involving altered fibroblasts, extracellular matrix, inflammatory signals, blood supply and immune cells.

Put simply, the sarcoid is not just a lump. It’s a living tissue environment that knows exactly how to sustain itself. This helps explain why sarcoids can behave so differently from one horse to the next, and why removing what we can see doesn't always mean that every altered cell has gone.

The six recognised forms

Veterinary texts commonly describe six clinical types. A horse can have one form or a mixture, and a lesion may change over time.

1. Occult
   Flat, roughly circular areas of hair loss or altered, slightly scaly skin. These can be mistaken for rubs, ringworm or old scars, particularly in their early stages.
   
   
2. Verrucose
   Dry, scaly or wart-like lesions with an irregular surface. They may be slow-growing but can become more active following trauma.
   
   
3. Nodular
   Firm, defined lumps beneath the skin. The overlying skin may initially look normal, although some nodules are attached to it or to deeper tissues.
   
   
4. Fibroblastic
   Fleshy, ulcerated or rapidly growing masses that may bleed easily. These often develop from another type after injury or repeated interference.
   
   
5. Mixed
   A combination of two or more forms within the same lesion or on the same horse.
   
   
6. Malevolent
   A rare, aggressive form that spreads extensively through the skin and along lymphatic pathways. This is not typical sarcoid behaviour, but it’s one reason why the statement “sarcoids never spread” is a bit too sweeping.

Location matters just as much as appearance. Lesions around the eye, mouth, sheath, groin, lower limbs or other anatomically difficult areas can become serious while still relatively small.

BPV – the trigger, but not the whole story

Bovine papillomavirus is the strongest and most consistent biological thread running through equine sarcoid research. But here’s the curious bit - BPV DNA has also been detected in normal-looking skin, in horses both with and without sarcoids.

Which means – exposure is not the same thing as disease.

The most useful way to think about BPV is as a necessary or highly important trigger in most sarcoids – but not, by itself, a complete explanation of why a visible tumour develops.

Researchers now describe a far more layered process. Viral proteins can interfere with normal cell regulation, encourage fibroblast proliferation, and reduce the cell's visibility to immune surveillance. At the same time, the surrounding tissue may be remodelled in ways that help those cells persist, invade locally and establish a blood supply.

That's why a recent scientific review described sarcoids as a virus-initiated, host-sustained tumour.

I quite like this phrase, because it moves us past the old idea of “virus arrives, lump appears”. The virus may light the match, but whether a lasting fire takes hold appears to depend on the horse and the biological ground on which that match lands.

So why this horse? This is the question that matters – and it’s also one that science can’t yet answer completely.

Genetics – susceptibility, not destiny

It’s thought that sarcoids occur more frequently in some breeds and family lines, with  research having identified associations with regions involved in immune function, including the major histocompatibility complex. (Cornell University’s Genetic Studies of Equine Sarcoid Tumors page: https://www.vet.cornell.edu/departments-centers-and-institutes/baker-institute/research/genetic-studies-equine-sarcoid-tumors)

The 2026 international consensus statement estimates heritability at at least 20%, while stressing that susceptibility is likely to be polygenic – meaning involving multiple genetic influences rather than one simple “sarcoid gene”.

So yes, as per an enquiry we had just last week regarding numerous sarcoids in a mare and then lesions in her daughter, it's perfectly reasonable to wonder about inherited susceptibility - but it doesn’t necessarily mean the filly has inherited an inevitable future.

What may be inherited is a tendency in the way viral material is recognised, immune signals are organised, skin repairs itself, or fibroblasts respond. Genetics may load one part of the dice, but they don’t dictate every throw.

And… there’s another intriguing layer. BPV DNA has been found in placental tissues and in samples from mares and foals, raising questions about possible prenatal exposure. That is interesting research, but finding viral DNA is not the same as proving that an active infection – or a future sarcoid – has been passed from mother to foal.

For now, family history is best treated as useful context, not a crystal ball.

Immune surveillance - when altered cells slip beneath the radar

The immune system does far more than fight infection. Amongst other duties it patrols tissues, recognises damaged or abnormal cells, and helps decide what should be repaired, tolerated or removed.

Meanwhile, BPV is clever – a bit like the Lyme bacteria, Borrelia burgdorferi – they’re both particularly good at interfering with the immune system’s surveillance. It’s clever enough that one of its proteins can even reduce the cellular “identity cards” that help the immune system inspect and recognise altered cells (MHC class 1 molecules).

So if I was explaining this over the yard gate with a cuppa, I’d probably say that if an altered cell keeps its head down and removes its name badge, the patrol is rather more likely to walk past.

This also doesn’t mean a horse with sarcoids has a universally weak immune system – which is what I historically hinted at. A horse may cope perfectly well with ordinary infections while still having a very specific gap in antiviral or tumour surveillance within the skin.

This distinction matters, because “boost the immune system” – again what I historically suggested - is now a bit basic. Not altogether bad – it always helps to be mindful - but immune biology is a bit bigger than this. It’s about recognition, balance, timing and communication – not simply turning a volume knob upwards.

The local environment - why skin and tissue context matter

Sarcoids often appear - or become more active - at sites of skin damage, rubbing or repeated irritation. Flies have long been suspected as the most likely carriers of BPV, while wounds can create a local environment rich in repair signals and rapidly active fibroblasts – precisely the cells involved in sarcoid development.

None of this means every wound will become a sarcoid, or that an owner caused one by missing a tiny scrape – far from it. But it can mean that in a susceptible horse, trauma and tissue repair may sometimes help open a small biological window of opportunity – which is what the dormant virus is waiting for.

Here’s where our central question returns - could the visible lump be the final event in a chain that began with exposure, susceptibility and a changing local environment?

This is where the thinking is now. We can’t yet identify every link in that chain, but looking for the chain is more useful than treating the lump as though it appeared all by itself.

And what about the gut, stress and the wider horse?

This is where we need to keep one foot firmly on the science and the other open to a developing whole-horse picture, as there’s currently no clinical evidence proving that gut dysbiosis, stress, liver function or a particular dietary pattern causes equine sarcoids. Nor has research identified one management factor that reliably predicts which BPV-exposed horse will develop them.

However, the gut, metabolism, nervous system, skin and immune system are not separate little departments operating behind closed doors – they communicate constantly with each other. Chronic gut disturbance, pain, psychological stress, inadequate nutrition and wider metabolic strain can all affect immune signalling and tissue repair in general physiology.

This wider “terrain” approach is also reflected in the work of equine biologist Dr Christina Fritz and Sanoanimal. Their clinical model asks whether gut dysbiosis, chronic stress and wider metabolic pressure can leave the immune system with less capacity to keep latent viral patterns and altered skin cells contained.

It’s a biologically plausible and useful supportive model, while not necessarily proof of a direct causal pathway. That said, this is the lane I'm personally most comfortable in.

We don’t need to declare that every sarcoid began in the hindgut. But we absolutely can acknowledge that a well-nourished, metabolically steady horse with a resilient gut and as little chronic stress as realistically possible, is better supported for the long game than one whose system is permanently firefighting elsewhere. Just physiology being allowed the best working conditions we can give it.

Why do sarcoids so often return?

Back to Charlie and that eyelid.

Each time the visible growth was banded, it disappeared. Yet the biological conditions that allowed it to exist may not have changed – and microscopic altered cells clearly remained beyond what we could see. Bear in mind I was not much older than 12 at this time, so I certainly wasn’t looking any deeper than that horrible lump!

But a few decades later? We now know that sarcoids can extend into surrounding tissue with poorly defined microscopic margins. Some treatments remove or destroy the visible mass but do not reach every affected cell. Other lesions may be reactivated by inflammation or trauma. We also know that location can limit how aggressively a vet can treat, and each sarcoid's microenvironment may also respond differently. All part of what makes these tumours so challenging.

It’s also why there’s no universally "best treatment". A 2023 systematic review found the published evidence for most sarcoid treatments to be low or very low in certainty. Several approaches can achieve excellent results in selected cases, but studies vary enormously and direct comparisons are limited.

The right question is therefore not, “What is the best sarcoid treatment?”, but “What is the best approach for this sarcoid, in this position, on this horse, at this point in time?”

Veterinary treatment

Depending on the lesion, its location and the facilities available, veterinary options may include:

• careful monitoring of selected quiet lesions;
• surgical or laser excision;
• cryotherapy;
• radiotherapy;
• topical or intralesional chemotherapy;
• electrochemotherapy;
• immunotherapy, including BCG in selected periocular lesions;
• or a planned combination of approaches.

No one option is suitable for every horse - your vet may recommend referral, imaging, biopsy or treatment without biopsy depending on the appearance and location.

Meanwhile, histopathology remains the definitive way to identify tumour tissue (the microscopic examination of a skin tissue sample by a pathologist to confirm a definitive diagnosis of the tumor - but biopsy is not a casual DIY decision. Disturbing a sarcoid can sometimes stimulate more aggressive behaviour, so the diagnostic plan belongs with a vet who can act on the result and manage the lesion appropriately.

Ask your vet promptly if:

• the lesion is near an eye, eyelid, mouth, sheath, groin or joint;
• it is growing or changing quickly;
• it has become ulcerated, painful, infected or is bleeding;
• tack or movement repeatedly rubs it;
• there are several lesions appearing in a short period;
• you are unsure whether it is a sarcoid at all.

And remember – a photograph on social media, however enthusiastically inspected, is not a diagnosis - many skin conditions can also mimic one another.

What you can do alongside your vet

This is where thoughtful daily management earns its place.

1. Photograph, map and measure

Take clear photographs from the same angle, i.e. a ruler or coin. Note the date, exact location, surface changes and any treatment. Sarcoids can alter slowly, and if you’re anything like me, memory may not be the best measuring device. 😉

2. Reduce rubbing, trauma and flies

Protect vulnerable skin without repeatedly irritating the lesion. Use sensible fly management, clean equipment and prompt wound care.

 

3. Resist aggressive home remedies

Back in the day it was thought that toothpaste was a good remedy! Caustic substances and unplanned “natural” preparations can cause inflammation, pain and rapid deterioration while delaying effective treatment.

Sarcoids are famous for objecting to interference, and remember - natural doesn’t’ always mean gentle – chilli is natural, and I wouldn’t put that on my eyelid either. 😉

4. Be boringly good with the nutritional foundations

Adequate protein, copper, zinc, selenium, vitamin E and other micronutrients matter to normal immune function, collagen formation, antioxidant defence and skin repair. A forage-led diet with an appropriate mineral foundation is far more useful than chasing a single fashionable ingredient.

It won’t treat a tumour though – it simply makes sure the horse is not being asked to maintain skin and immune function with half the toolbox missing.

5. Look at the wider pattern

Does this horse also have persistent loose droppings, recurrent skin problems, chronic stress, poor hoof quality, allergies, repeated infections or other signs that the biological terrain could be steadier?

These patterns won’t prove the cause of a sarcoid, but they may tell us where sensible supportive work belongs.

6. Think in months, not days

Veterinary treatment may act directly on a lesion, while nutritional and whole-horse support do something different – they help create more favourable conditions around normal immune, skin and connective-tissue function.

Which is slow work. Anyone promising overnight prevention or disappearance is offering certainty that sarcoid biology simply doesn’t give us.

Can anything really prevent future sarcoids?

Honest answer? At present, nothing has been proven to prevent every future sarcoid.

Vaccines are an active area of research, but prophylactic and therapeutic BPV vaccines are not yet part of routine clinical practice. There’s no feed supplement, topical preparation or management programme that can provide a sarcoid forcefield.

I know that answer isn't as satisfying as a guaranteed protocol, but honest uncertainty is far kinder than selling false hope. What we can do is reduce avoidable pressure and support the systems involved:

• manage flies and skin trauma as practically as possible;
• provide sound nutritional foundations;
• address chronic gut disturbance, pain and stress where they exist;
• support healthy skin, connective tissue and balanced immune function over the long term;
• continue monitoring, including areas where previous sarcoids have been treated.

This isn’t the same as proven prevention, but it is a careful attempt to make the biological window of opportunity as small as we reasonably can.

Where EquiNatural’s SarcoShield fits

SarcoShield was developed for owners who want to support the horse beneath the sarcoid – particularly where there are existing lesions, recurrence or a family pattern that makes long-term resilience feel especially important.

It combines:

• Barleygrass – providing whole-plant phytonutrients and antioxidant support;
• Rosehips – supporting antioxidant status, collagen formation and normal connective-tissue maintenance;
• Pau D'Arco – traditionally used as part of wider botanical support for immune and internal microbial balance.

Its role is to support healthy immune function, skin integrity, connective-tissue resilience and the horse's wider biological terrain. It is not a veterinary treatment, and we cannot promise that it will remove an existing sarcoid or prevent another one appearing.

This is also not a quick-results blend. Based on the long-term experiences owners have shared with us, I would view at least twelve months as a realistic commitment, used alongside veterinary monitoring.

This length of time can be disheartening when the sarcoid you can see is still sitting there doing apparently nothing – I get that. But the work we’re asking the horse’s inner engine to do – normal tissue turnover, collagen support, antioxidant defence and immune regulation – runs to biological timescales, not delivery-tracking ones.

The experience that helped shape the blend

Part of the inspiration came from Caroline Ingraham's published case experience in which a horse with sarcoids repeatedly selected barleygrass and rosehips over a long period.

We have since seen similarly slow, individual owner experiences – including one mare whose changing preference for these plants was followed over many months alongside a photographic record of her sarcoids.

Agreed, while these stories aren’t clinical trials and shouldn’t be presented as proof, they are, however, part of the observational trail that led us to ask whether sustained nutritional support for skin, connective tissue and immune resilience deserved a thoughtful place beside veterinary care.

For me, this is exactly where SarcoShield belongs: not attacking the visible lump, and never replacing the vet, but supporting the biological ground beneath it for the long haul.

Do we ever look beyond SarcoShield?

Yes – because the horse may be telling us a wider story.

The answer is not automatically more products. Where sarcoids sit alongside persistent gut imbalance, poor skin or coat, allergies, recurrent infections, difficult recovery or several chronic patterns, it may be worth stepping back and reviewing the horse's forage, mineral foundation, stress load, gut function and broader health with an appropriately qualified professional.

Sometimes it might be better forage analysis, or correcting a mineral shortfall, addressing pain, improving turnout or companionship, investigating a digestive problem, or asking the vet to look for something we haven’t yet found.

And sometimes, after all that detective work, the sarcoid still behaves like a sarcoid – because horses do enjoy keeping us humble don’t they…

A few common questions

Are sarcoids contagious?

Sarcoids don’t behave like a straightforward contagious disease passing freely from horse to horse. Current evidence suggests that sarcoid tissue contains viral DNA but not readily detectable infectious virus particles, and cattle are considered an important source of BPV exposure, with flies possibly acting as carriers.

There's still uncertainty around transmission, so good fly control, hygiene around ulcerated lesions and avoiding transfer of blood or tissue between lesions are sensible precautions.

Is a sarcoid cancer?

It's an equine skin tumour. Most sarcoids are locally invasive and don't metastasise to distant organs in the usual way, but they are not harmless cosmetic warts. Their location, recurrence and response to trauma can make them clinically serious.

Should every sarcoid be removed?

No. Some quiet lesions may be monitored, while others are best treated early because of their site or behaviour. Treatment itself can provoke change, so this should be an individual veterinary decision rather than a blanket rule.

Can sarcoids disappear by themselves?

Spontaneous regression can occur, particularly in younger horses and milder disease, but it's unpredictable and shouldn't be relied upon for a growing, ulcerated or badly positioned lesion.

Can SarcoShield be fed during veterinary treatment?

It is designed as nutritional support rather than a replacement for treatment. If your horse is receiving medication, chemotherapy, immunotherapy or has another medical condition, show your vet the full composition before starting any supplement.

How quickly should I expect a change?

There is no reliable timetable, and visible change is not guaranteed. SarcoShield belongs in a long-term plan; we suggest thinking in terms of at least a year rather than a few weeks.

The bottom line

Sarcoids begin with a virus – but the virus isn’t the whole story.

The lesion we see appears to emerge from an interaction between BPV, susceptible cells, genetics, immune recognition and the local tissue environment. We’re still learning exactly how those pieces fit together.

This is why our approach needs two clear routes:

1. The sarcoid itself needs early, individual veterinary assessment and carefully chosen treatment or monitoring.
2. The horse underneath it deserves strong nutritional foundations, good skin and gut care, manageable stress, thoughtful observation and realistic long-term support.

We can’t promise prevention, nor can we promise that a blend will make an existing tumour disappear. But we can stop treating the visible lump as though it exists in a biological vacuum.

And perhaps that's the most useful shift of all. Not “How do we attack this sarcoid harder?” but “How do we manage the lesion wisely while giving this horse the strongest, steadiest ground we can beneath it?”

Mug down, camera out, long game begun 😉

Sources & further reading

• World Association for Veterinary Dermatology. Equine Sarcoid Consensus Statement (2026).
• RCVS Knowledge. Treatment of equine sarcoids: a systematic review (2023).
• UC Davis Center for Equine Health. Sarcoids.
• Cornell University College of Veterinary Medicine. Genetic studies of equine sarcoid tumors.
• PubMed. Equine sarcoids: Virus-initiated, host-sustained tumors – recent advances in molecular pathogenesis (2026).
• Sanoanimal / Dr Christina Fritz. Sarcoids and melanomas – causes, management and wider support (German).
• Dr Christina Fritz, Natural Horse Issue 33 (2021). Sarkoide beim Pferd – mehr als nur ein Schönheitsfleck (article preview; German).