(1) Wind-heat pathogen invades the lung, or wind-cold turns into heat. Pathogenic heat accumulates in the lung, heat toxin burns the lung, and heat is trapped in blood stasis, resulting in carbuncle, blood failure and pus.

(2) Deficiency of healthy qi and excess of phlegm heat; Or excessive drinking, improper diet, overeating spicy taste, leading to internal heat, wind-heat pathogen and toxin recurrence, internal and external evil knot.