In TCM terminology the "exterior" refers to the first level of impact a disease has on the body. This area is protected by the "wei qi" or "defensive qi". An example of the distinction in disease is the difference between a mild cold and a cold going quickly to bronchitis. In one case the condition was left on the exterior and resolved by the immune system, in the other it was allowed to go much deeper internally and cause more significant health issues. From a treatment perspective disease is always most efficiently treated at the earliest possible stage. Appropriate treatment for acute symptoms, then, will lead to good results. As the condition is allowed to linger and deepen you must choose between release it via the exterior or treating the internal imbalance. This is an important distinction as releasing the exterior with an internal deficiency can lead to further health issues, possibly even deepening the condition. The majority of these formulas are best used for relatively acute symptoms and will encourage to varying degrees the person to release the pathogens via sweat.