Horse skin seems prone to many problems characterized by a lump, bump, nodule, or swelling. To make identifying the cause of your bump easier we have to refine our vocabulary a bit. As we better define the meanings the list of possible disease grows shorter for each term:

• Papule: a small (1 cm or less) firm palpable mass.
• Nodule: a large (1 to 3 cm) firm palpable mass.
• Tumor: a very large (> 3 cm) mass.
• Cyst: a flucuent well descibed mass usually indicating a fluid filled sack.
• Wheal or Hives: a small to fairly large focal swelling of the skin that pits when pressed.
• Blister (or vesicle): Swelling on the surface of the skin or mucous membrane filled with clear serum. When it burst it leaves behind a erosion or ulcer.

Let's diffentiate the above from swellings. Swellings are when fluid accumulates under the skin, and cause a focal or generalized enlargment by pushing out on the skin. Swellings are covered in their own article...more.

Because there are many different common causes for bumps, the only sure way to know what a bump is requires removal and laboratory exam. However, you can get pretty close to an accurate diagnosis by careful examination and history on many bumps. This report helps differentiate the major causes of lumps and bumps in horses by their appearance and how they behave and provide treatment quidelines. Links are provided to more specific disease articles.

• Those That Don't Look Irritated or Bleed
  • Chronic Fly Bite Reactions: Nodular Necrobiosis
  • Aural (Ear) Plaques
  • Warts
  • Melanomas
  • Hives
  • Sarcoids
  • Equine Cutaneous Amyloidosis
• Those That Appear Irritated or Bleeding
  • Sarcoids
  • Habronemiasis or Summer Sores
  • Proud Flesh
  • Squamous Cell Carcinoma
• Nonpainful Swellings or Lumps Under the Skin (the skin moves freely over the lump)
• Hot Painful Swelling Under the Skin