If you have a horse that develops air under the skin and thus looks like someone has inserted an air hose there, know that there are several conditions that can lead to this appearance.  The most common cause of subcutaneous emphysema, or air under the horse’s skin, is a laceration in the axillary area between one of the forelimbs and the chest.  A deep laceration in this area can dissect upwards deeply between the chest wall and the front leg and allow air to enter the tissue, usually 3-4 days after the injury.  Although air can enter the tissue, the tissue acts as a one-way valve and prevents the air from escaping, so as the horse moves more air enters the wound area and air begins to build up under the skin. 

These horses can look really strange. Although most of the time the air will eventually be resorbed (sucked back in) on its own, sometimes it can lead to a serious problem.  The air can enter the structures inside the chest cavity and can even be deadly by leading to pneumothorax, a condition that prevents the horse’s lungs from expanding.  It is also possible the air can carry bacteria and spread the infection over the entire body under the skin. 

Although it seems you could just stick a needle in the horse’s skin and remove the air, it doesn’t work that way as the air is actually in the tissue and cannot be removed with a needle.  Treatment involves decreasing the horse’s activity level to prevent further air accumulation and to temporarily seal the incision by packing it with sterile material that can be changed every other day. Most of these horses also need to be on antibiotics for infection control. Trauma to the respiratory system or to the esophagus can also lead to air trapped under the skin but is much less likely than a laceration under the front legs.  The air will eventually resorb in most cases but may require 3 about weeks to do so.