Differentiation of yin and yang is the main guiding principle for diagnosingexternal diseases, particularly wound infections. They help to decide the therapeutic methods to be used, to predict disease development as well as the prognosis of the condition. Generally, yang syndromes have more favorable outcomes.

	Yang syndromes	Yin syndromes
	Acute	Chronic
	Located superficially on the skin and in the muscles	Located deeply in the bones and tendons
Localized conditions	Skin turns red	Normal or dark-purple skin color
	Scorching heat	Only mild heat
	Protruding swelling	Flat or collapsed swelling
	Confined area	Diffuse and extensive
	When newly formed, the area is firm but gradually turns soft after ulceration.	When pressed, the area feels either solid or soft.
	Very painful	Dull pain, soreness or no pain at all
	Thick, sticky pus	Thin, watery pus
	New tissue is red and tender.	New tissue is darkish and purple in color
Systemic conditions	There are chills and fevers, thirst, constipation and yellowish urine in the initial stage.	No obvious symptoms in the initial stage, but after the site becomes ulcerated, there may be virtual fire signs or signs that suggest that blood and qi are insufficient.
Tongue andpulseobservation	The tongue is red and covered by yellow coating; the pulse is strong.	The tongue is pale and covered by white coating; the pulse is weak.
Duration	Short	Long