It may occur when the body is exposed to wind when it sweats and invaded by pathogenic wind-cold or wind-heat that causes accumulation of pathogenic factors in the skin and striation due to constitutional intolerance and failure of Wei-Defensire Qi in protecting the exterior; or when pathogenic dampness and heat are accumulated in the spleen and stomach due to improper food intake or insect accumulation plus invasion of pathogenic wind.

If the skin can not be nourished due to prolonged illness leading to deficiency of qi and blood or insufficiency of Ying-Nutrient Qi and blood caused by disharmony between the Thoroughfare Vessel and Conception Vessel; if excessive heat exists in Qi-Energy System and Ying-Nutrient System, transformed from fire due to internal attack of medication toxin or invasion of pathogenic toxic factor, and if yin is damaged by fire due to stagnation of the liver qi in emotional disturbance plus invasion of pathogenic wind. The acute attack is mostly related to strong anti-pathogenic ability and excessive pathogenic factors and the disease can subside after the pathogenic factors are gone. If qi and blood become deficient after long duration, the disease is often in a chronic tendency with easy recurrence.