When you have just caught a cold, you will have the symptom of a runny nose. At this time, the snot is clear and transparent like egg white clear snot, this symptom indicates that the cold evil has attacked the body surface, is developing into the body. This is the first stage of external infection. When the cold evil invades into the body, the color of the runny nose will gradually worsen, from clear to yellow. Changes in the symptoms of the runny nose represents the process of cold evil from the body surface to the invasion of the body, in this process, the color of the snot will change from clear to yellow and then white, like white latex paint like white snot often in the cold almost good time will appear.