Conditions or ailments that are the cause of a problem that you see - your observation.

Your vet may diagnose

Nodular Necrobiosis or Eosinophilic Granuloma

Synonyms: Collagen Granuloma, Collagen Necrosis


This common condition has many complex-sounding names. It is the most common skin condition that presents as multiple small lumps and bumps and it is most common over the back and withers. These are hard, pea-sized bumps under the skin, with no hair loss in most cases.

The cause of this disease is not entirely understood. It is an inflammatory, hypersensitivity-like disease. It is more common in spring and summer and insects allergy may be involved. Because of the common location, under the saddle, and the fact that it is more common in ridden horses, it is thought that pressure from the saddle may be a factor.

Diagnosis is often made just by the typical appearance of the condition, i.e. multiple small firm bumps along the skin of the back and withers. But definitive diagnosis requires biopsy and submission to the laboratory.

Treatment is usually injection of steroids under the bumps, or surgical removal.

my vet's role


The prognosis is good. The nodules don't usually cause the horse much problem, although large ones can become painful under the saddle.

my role

Questions To Ask Your Vet:
  • How can we prevent this condition from recurring?

There is no known way to prevent this condition in horses that are predisposed to developing it.

Insects should be controlled to reduce insect allergy. Ensure good saddle fit to reduce focal pressure on the skin of the back.

further reading & resources

Related References:

Equine Dermatology, Scott, DW, Miller WH eds. Saunders:Missouri, 1st ed. 2003.

Author: Doug Thal DVM Dipl. ABVP