Upashya is very useful to ascertain the nature of the
disease. For example, when the doubt arises regarding the nature of the
predominant dosha i.e. whether it is vata dominance or pitta dominance
or kapha dominance, then upashya comes into play. Learn more about
Upashya in the link below:
http://www.indianetzone.com/17/upashya.htm
http://www.indianetzone.com/17/upashya.htm