Surface issue

The skin is the largest organ in the horse’s body and its job is to provide a barrier between the outside world and the internal structures, protecting your horse from physical and microbiologic (bacteria and viruses) harm. It also contains nerves that allow the horse to perceive temperature, pain, pressure and touch. As such, it has an important job but, by being in direct contact with so many external influences, it’s vulnerable to its own issues.

Skin deep

A horse’s thickest skin is on the forehead, neck and hindquarters, and thinnest on the ears, armpits and underneath the tail, but, on average, a horse’s skin is 3.8mm thick and is formed of the following three layers…

1. The epidermis forms the outer layer and contains many cell types responsible for protection, immune response, skin colour and sensation.
2. The dermis is the thickest layer. It contains connective tissue, blood vessels, nerves, hair follicles and the glands that produce oil and sweat. It gives skin its structure and also contains immune cells to fight infection.
3. The subcutis is the deepest layer, lying over muscle, and contains fat to provide insulation, some muscle cells, nerves and blood vessels.

Bumpy and lumpy

Lumps and bumps on the skin of horses are not uncommon. Those most usually seen include…

• sarcoids, which are the most common skin tumour in horses and can affect any equine. There are six types and their appearances range from thickened skin to ulcerated, bleeding lumps. They often develop on areas where there’s thin skin
• melanomas, which most frequently affect older, grey horses (approximately 80% of grey horses over the age of 15 will have one). They usually appear as black, shiny, hairless lumps and often grow under the tail, around the sheath, udder, face or lips. They can also grow internally around organs, and can have huge implications for a horse’s welfare
• squamous cell carcinomas, which are usually seen around the eyes and external genitalia. They affect pink skin that’s had overexposure to sunlight and can become ulcerated, leading to painful infections
• papillomas, which are warts commonly found on young horses. They develop from a viral infection and appear as small, grey bumps on the muzzle, face and legs, usually resolving spontaneously in a few weeks or months. They can also be found in the ears of young horses and often remain, but are usually only a cosmetic concern

Top tip

If a new lump has appeared or there’s a suspicious-looking lesion, call your vet for advice so treatment can begin as early as possible.

Discover more about common skin conditions in August Horse&Rider – out now!