It refers to an acute suppurative disease between the muscle and skin. It is believed in Chinese medicine that this disease is mostly caused by internal accumulation of toxins in zang-fu organs and secondary invasion of exogenous wind-heat, damp-heat and fire, which gather in the superficial muscle to cause obstruction in the meridians and collaterals, disharmony of Ying-Nutrient Qi and WeiDefensive Qi, and stagnation of qi and blood. Usually, it is believed that the condition of the patient's constitution is closely related to favourable and unfavourable prognosis.

It's clinical feature is that there is a millet grain-like pus dot on the tumefaction in the initial stage, with local burning sensation, red swelling and pain, and the tumefaction is easy to penetrate to the deep position and spreads around, with increasing pus dots. Mter ulceration ruptures, it looks like a lotus seedpod or honeycomb. The tipped ulcer occurring on the nape is also nicknamed head ulcer or mouth-opposite ulcer. The tipped ulcer happening on the back is called back ulcer or hand-touching ulcer. It is similar to carbuncle in Western medicine.