It is often very hard to determine whether a horse has a swollen tongue, unless it is so swollen that a horse allows it to protrude out of the mouth. In this case, the swelling may increase simply due to exposure to the elements.

A swollen tongue can result from infection, inflammation or injury. This can also be seen in horses with a neurologic dysfunction and exposure damage to the tongue, and horses in shock as they succumb to an underlying disease. Several times, I have seen a severe, apparent allergic or contact reaction to a common commercial deworming paste (ivermectin and praziquantel).

If the swelling is a result of trauma, the good news is that injuries to the mouth generally heal very quickly.