External Pathogen Qi has six types. They’re often called the Six Climatic Pathogens because they’re named after weather phenomena which possess similar characteristics. The six types are Wind, Heat, Cold, Damp, Dryness, and Summer Heat. Wind is a good example. When Wind enters the body (via the pores in the skin) it attempts to go where it wishes. Invariably this is contrary to the body’s healthy flow of Qi and so a struggle arises between the two which impairs or stagnates the flow of Qi.
You’ve seen trees in the wind. Wind can appear and disappear very quickly or it can blow steadily. If it’s the Lung Qi which is disordered there will be intermittent coughing or paroxysmal coughing. Wind can gradually burgeon in force and speed. And it moves from place to place. When the Wei Qi is disordered “flu aches” can occur and move from joint to joint. Sometimes a gentle breeze flutters the leaves and sometimes a gale bends the tree over and holds it there. Wind can also cause tremors or paralysis.
Heat and Cold are a bit more literal. Both manifest with their actual temperature sensations. They also produce colors in parts of the body; red face, red rashes, red tongue, rusty or red colored urine, and red swellings all indicate the presence of Heat. White, gray or clear indicate the presence of Cold.
This is a subset of Heat which occurs predominantly during the summer. It’s traits are severe heat signs.
This is moisture. Identifying charateristics are heaviness, thickness, moves downward. Damp excells at blocking Qi.
Lack of moisture decreases flexibility in many things. Dryness makes stuff brittle. Paper and bread are two good examples of this. Often bits and pieces of the dry object flake away.
Although these pathogens were identified long before the technology of climate control modern city dwellers are still at risk. Sleeping or working under a vent subjects you to wind. Automobile AC/heat systems set on high create Heat or Cold in extremes to quickly affect a small space. Living in Seattle or south Georgia exposes you to damp and winter in the southwest U.S. subjects you to dryness.