What Are Sarcoids?

Sarcoids are persistent fibrous growths that affect horses and come in multiple types. They are commonly seen as round nodules or warty clumps that grow, usually just under the skin, though they can ulcerate and become messy, especially in the summer. Some sarcoids grow slowly and cause few problems for the horse and their owner, but others can grow quite quickly and can require extensive treatment. They can be difficult to treat and unsightly, but are most problematic when they occur around the ears or girth area. 


Sarcoids appear to be caused by a virus, one of two types of a particular bovine papilloma virus (BPV), which is named that because they were initially thought to just cause warts (or papillomas) in cattle. In cattle, these very closely related viruses cause warts to grow on young cattle and then fade away as the cattle age and their immune system grows stronger. Very rarely, in cattle, the warts progress to become growths similar to sarcoids. However, there appear to be horse-specific variants of the virus, that are found in cattle and horses, that are responsible for sarcoids in horses. Usually, we would expect that a horse with a strong immune system would be able to fight off the virus and cause the growths to spontaneously recede, but horses with sarcoids are only very rarely able to do this. Research has shown that differences in the cells that make up the horse’s immune system may interact with the virus, and this may explain some of why some horses are severely affected with sarcoids and some are not, especially as many healthy horses have the virus but no sarcoids. It is suspected that the virus is transmitted by flies and possibly by contaminated equipment (for instance, a head-collar or brush which came into contact with an ulcerated sarcoid), particularly around wound sites or sites of other trauma, but direct transmission from horse to horse is less likely. As always, keeping equipment clean and separate for each horse is important!


We can treat sarcoids with specially formulated pastes that are applied by us, under licence. These formulations are much stronger than what can be found online, and can therefore only be applied by a veterinary surgeon. The pastes are made at Liverpool University and are ordered specially for every case after we have supplied photographic evidence of the sarcoid to be treated, and are supplied along with a customised treatment plan for each sarcoid. At the moment, there is no 100% successful treatment for sarcoids of any type, but we do know that the first cycle of treatment has the highest rate of success, and these cytotoxic pastes have the best rate of success over a variety of sarcoid types, sometimes in combination with other therapies.

Other treatments vary depending on the site of the sarcoid, the size, and how severe the sarcoid is, and also how difficult it will be to treat with the cytotoxic cream. The treatment with the highest rate of recurrence is to ‘band’ the sarcoid or to remove it surgically. ‘Banding’ involves placing a tight elastic band at the root of the sarcoid to cut off the blood supply, so the sarcoid gradually dies, shrinks and falls off. Surgical removal is faster, but can lead to scarring, and can lead to wounds that are difficult to heal as well as more sarcoids developing along the scar. Other treatments can include immune-stimulating injections into the sarcoid, placing cisplatin beads into the sarcoid (these are a form of chemotherapy) with or without UV light as well, or removing the sarcoid with controlled freezing by liquid nitrogen. This is a very complex and complicated area, however, so we advise talking over any plans of treatment with your vet surgeon for the best possible outcome. 

For more information, we recommend you obtain the following, via the University of Liverpool’s website:

Twenty Facts You Need to Know About Sarcoids
- a Guide for Vets and Owners

Dr Derek Knottenbelt BVM&S DVM&S MRCVS from The University of Liverpool in the UK, has written a guide for veterinarians and owners on equine sarcoids. The Guide has been produced in association with Intervet UK and the Home of Rest for Horses

The Guide covers everything from what a sarcoid is to predisposition, treatment and what an owner should consider before buying a horse with sarcoids. Each section is covered in an easy to read format with images showing the various types of sarcoids that occur. The Guide can be seen ::HERE on The University of Liverpool's website.


Phone us at Parkside if you have any problems and we can advise, or email us at This email address is being protected from spambots. You need JavaScript enabled to view it.
To receive a copy of the Guide, contact The University of Liverpool. Tel: +44 (0)151 794 6041