What we experience as a "cold" is our lymphatic system reacting as it should. Our body produces mucus from the mucosa (Inner lining of the body). Upon certain conditions, the mucosa will produce this mucus to buffer and protect the body.

Acids present in the body such as drinking a coke, or having a smoke, will cause the formation of mucus.

Our lymphatic system will attempt to release this from the body through all available channels. Our primary release is through the kidneys and so we should release a small amount several times a day. If it's plugged up, we will get what we refer to as a cold.

Cold temperatures activate the lymph as well as it is alkaline and our body tends to be too acidic due to our improper diet and lifestyle.

Plug up the muffler of a car and see what happens. It channels back the other direction and tries to find a way out. (Of course hat doesn't last very long!)