It can block channels, causing numbness. Phlegm can show up about anywhere in the body, but it's especially prone to show up in the Lungs. Phlegm can the cause of hundred diseases. Evil Spirit of hundred ailments is the Phlegm. In other words, Phlegm is very versatile in the problems it can cause.
Phlegm can figure into some very complex clinical pictures.
It can take a long time to resolve Phlegm problems once they get established, and especially after they've been around for a while. The main points to remember is that Qi Stagnation is one of the things which can produce Phlegm, and Phlegm can cause Qi Stagnation. The Spleen is the main culprit involved in the production of Phlegm, but the Lungs and Kidneys also frequently are culprits. Phlegm has a particular affinity for collecting in the Lungs, but it can show up anywhere in the body, including channels. Phlegm can create a lot of different problems throughout the body.