Aversion to cold and fever means that the patient dislikes cold and the body temperature increases, usually seen at the primary stage of exogenous disease, which pertains to external syndrome due to retention of pathogenic factors in the superficies and struggle between defensive yang and pathogenic factors. Aversion to cold is caused by invasion of pathogenic factors in the skin which affects the function of defensive yang to warm the muscles fever is caused by pathogenic factors encumbering the superficies and resistance of defensive qi against pathogenic factors. When the pathogenic factors are in the superficies, there is difference in aversion to cold and fever due to the difference of pathogenic factors in nature. Generally there are three types of aversion to cold and fever according to their degree.
 
Serious aversion to cold and mild fever:
Serious aversion to cold and mild fever indicate external syndrome due to wind-cold. Cold is a pathogenic factor of yin nature. When pathogenic cold invades the superficies, defensive yang is stagnated and the superficies lacks warmth, leading to serious aversion to cold. Cold tends to coagulate. So when defensive yang is stagnated and when pathogenic factors struggle with healthy qi, fever is caused.
 
Serious fever and mild aversion to cold:
Serious fever and mild aversion to cold indicate external syndrome due to wind-heat. Wind-heat is a pathogenic factor of yang nature. When pathogenic factor of yang nature causes disease, yang is usually superabundant. That is why fever is serious. When wind-heat invades the superficies, the muscular interstices become loose. That is why aversion to cold is mild.
 
Mild fever and aversion to wind:
Mild fever and aversion to wind indicate external syndrome due to wind attack. Aversion to wind means sensation of cold in contact with wind and is relieved after avoiding wind, usually caused by exogenous pathogenic wind. Since wind tends to open, muscular interstices become loose when attacked by wind. That is why there are mild fever and aversion to wind.
 
The degree of aversion to cold and fever in external syndrome is not only related to the nature of pathogenic factors, but also to the relation between pathogenic factors and healthy qi. For example, if both the pathogenic factors and healthy qi are in predomination, aversion to cold and fever are all serious, signifying drastic struggles between healthy qi and pathogenic factors. When both pathogenic factors and healthy qi are deficient, aversion to cold and fever are all mild, indicating slight struggle between healthy qi and pathogenic factors. When pathogenic factors are superabundant and healthy qi is deficient, aversion to cold is serious and fever is mild, suggesting failure of healthy qi to control pathogenic factors.