Horse advice for lumps and bumps

Horse advice for lumps and bumps

Horses can suffer from a variety of lumps and bumps, some more serious than others. Equine veterinary expert Gil Riley explains what causes them and what action to take.

Lumps, bumps and swellings can vary in shape, size and appearance, and may be temporary blemishes or a permanent disfigurement. They can be anything from a small harmless bump to a large oozing sarcoid.

When diagnosing a lump in horses, it’s important to start with the history including when the lump was first spotted, whether it has changed in size, how it was caused, whether it is oozing or bleeding, if it’s painful and the general health of the horse.

Once your vet has all the information, and has made a physical exam of the lump, they can then attempt to work out the cause and solution for your horse.

Sometimes, samples of the lump are taken to further investigate its nature. For bony lumps and bumps on the limbs, your vet may use diagnostic tools such as X-rays to examine the underlying structures.

Common lumps and bumps found on horses include the following…

Heat and swelling

Bumps and lumps in horses that are swollen and feel hot to touch are usually due to trauma such as a kick from another horse. They are often accompanied by a cut or scratch.

A traumatic lump is due to swelling between the cells of the tissues, along with pooling of blood and inflammatory fluid.

A common example of this type of swelling is a haematoma, where a pocket of blood develops, or a seroma in the case of inflammatory fluid pooling instead. These pockets of fluid are sometimes drained to allow the injury to heal more quickly and to reduce scar tissue. Swelling caused by trauma usually resolves with time.

Any heat and swelling should be checked by your vet. Injuries that feel warm or hot to the touch can be treated with cold hosing or applying ice packs. Broken and bleeding skin will need to be cleaned, and you should call the vet if the wound is deep or bleeding profusely. To find out more about first aid, click here.

Insect bites

Biting insects, flies, ticks and midges can all cause a small, raised swelling on the skin that will often have a small scab in the middle. These may or may not be itchy – when itchy, bacterial infections can follow if your horse is rubbing or traumatising the area. Preventing insect bites is the best approach by using fly rugs, masks and fly repellent.


Hives, more precisely called ‘urticarial reaction’, are swellings that usually appear on the neck, withers and back of a horse's body, and are due to an allergic reaction. They occur more commonly in the summer months and are the result of reactions to insect bites, airborne or food allergens or heat.

Hives are recognised as flat, wide lumps on horses, giving the skin a wrinkled appearance. They will often sink into the skin when pressure is applied to them, and can be very itchy. In acute cases, itching will increase, swelling develops, and in severe cases, the hives can even interfere with breathing.

While neither preventative nor a cure, cold hosing can help to soothe symptoms such as heat and irritation. If your horse shows signs of pain or discomfort, you should seek veterinary advice immediately.

Collagen Lumps

Like hives, collagen lumps also occur as a result of an allergic reaction. They are not as painful as hives, and while starting soft, they develop into firm circular bumps, usually around 5mm in diameter.

They often appear at the site of a previous trauma, such as an insect bite, and are particularly common in the saddle area. It is believed that the damage to the collagen in the skin is caused by an allergic reaction being exacerbated by the saddle pressure.

The lumps themselves are not sore, but when in the area of the saddle, the tack and rider can force the hard lump against the underlying muscle of the back, causing discomfort. Although it sounds drastic, the lumps are very effectively dealt with by coring out with a small biopsy punch. The resulting wound can then be left unstitched, as it closes within days.

Pressure bumps

As the name suggests, pressure bumps are caused when pressure and friction damage tissue layers under the skin, which results in lumps of dead and damaged tissue. They are often found under the saddle area and where the girth sits, but can also show up anywhere there is tack.

These bumps feel firm to touch and vary in size, although they don’t usually get much bigger than a £1 coin, and horses very rarely feel any pain from them. They can signify poor-fitting tack, so a visit from the saddle-fitter is called for.


Often found under the horse’s tail or in the throat and neck area, melanomas are raised, dark pigmented or grey masses, commonly seen in older (over the age of nine years) grey horses. Normally slow growing, many horses can live with them, but there are various treatments available to remove them.

Squamous cell carcinomas

Manifesting as raised, irregular lesions, squamous cell carcinomas are often solitary and can become ulcerated. Found anywhere on the body, they are commonly seen in non-pigmented or poorly haired areas, and mucous membranes, such as around eyes, lips, nose and on the sheath or vulva. They are malignant and veterinarian attention is essential.


Sarcoids are a type of skin cancer in horses and are very challenging to treat and manage. There are six types of sarcoid:

  • Occult sarcoid – these are roughly circular, flat and can be hairless or have alteration of the hair growth. Sometimes, the skin may be thickened slightly.
  • Verrucous sarcoid – wart-like lesions, this type of sarcoid often have a grey or scaly appearance.
  • Nodular sarcoid – can be single or multiple lumps, circular in shape and often attached to the underlying skin or the underlying tissue.
  • Fibroblastic sarcoid – these are fleshy, raised growths that bleed easily and look like granulation tissue.
  • Mixed sarcoid – these are combinations of the above lesions.
  • Malignant sarcoid – fortunately very rare, these are lesions that have spread into the skin and subcutaneous tissue, and are more extensively invasive.

Sarcoids are tricky to treat and will often respond to treatment by increasing in size or spreading, making biopsy and removal of these growths difficult. Treatment of a sarcoid is best advised by your vet, as there are multiple treatment options available, and location and size can determine the treatment plan.

Has your horse ever suffered from lumps or bumps? If so, head to our Facebook page and let us know how you managed it.