Inflammatory airway disease (IAD), also referred to as lower respiratory tract inflammation (LRTI), is a common cause of poor respiratory health and reduced performance; affecting up to 50 percent of athletic horses, across all equestrian disciplines. IAD is characterized by airway inflammation and airway hyperresponsiveness, in addition to exercise intolerance, nasal discharge, variable coughing, and increased mucus in the airways.

IAD is considered to be a milder form of equine respiratory inflammatory disease, in which no respiratory effort is apparent while the horse is at rest. Both IAD and recurrent airway obstruction (RAO) also known as 'heaves', are caused by exposure to particulate matter. However IAD can affect horses of any age and is associated with more subtle clinical signs and RAO occurs in more mature, older horses with more obvious clinical signs.