THE ROLE OF DOSHA IN AYURVEDA

*. Nature and manner of vitiation of dosha
Doshas become vitiated in various manners. The nature of formation of a disease changes according to the nature and manner of vitiation.
*. Etiological factors of vitiation of doshas
Mildness or severity of the vitiation of dosha mainly depens upon etiological factors. If the factors are strong and many the vitiation is also strong. The duration of contact is also important in this connection. Contact for a long period is more dangerous than an occational contact. Regarding aganthu causes like krimi (pathogenic organisms) they cause vitiation of various kinds of according to this virulence or non-virulence.
*. Types of vitiation of doshas
* Prakrutha (normal) & Vikrutha (abnormal)
* Dependant & Independent
* Vitiation of dosha similar to the constitution and that of dosha dissimilar to
the constitution.
* Vitiation pertaining to a tract and that pertaining to gathi.
* Different combinations of doshas dual and triple.
*. Sama or Nirama type of dosha
A consideration of this also is essential.
*. Vitiation & Etiological factors
Vitiation of dosha occurs due to aggravation of their various qualities according to the etiological factors concerned.
E.g.:- Over exertion will vitiate vata by increasing the ruksha quality, while coldness will increase the sitha quality.Sour diet will increase the quality of pitta while solar or any kinds of heat will increase the ushna or hot quality of pitha.
The formation of samprapthi differs according to the quality of vitiation.

II. Nature & manner of spread of doshas.
He presence of dosha in koshta, sakha & marma cause pathological conditions which becomes more and more complicated and serious in that order.
It depends on the nature and type of the factor which causes the spread, such as over exertion, sharpness of agni,abnormal food and behaviour, force of vata etc. If many factors are responsible for the spread it will be quicker and will also proceed towards the deeper sakhas like asthi, majja and sukra or even towards marmas like heart and brain.The curability or incurability of samprapthi is related to this factor and hence it of great importance in diagnosis and prognosis.

* ROLE OF DUSHYA
Dushyas include dhatus, malas and srothases. Vitiation of doshas alone will not produce sammurchana unless there is a suitable ground in the farm of an abnormality and vitiation of srothes.
It is the vital stage in the formation of dosha dushya sammurchana. Just like a traveler first takes shelter in a waiting room and then starts activities like coocking washing etc. The vitiated doshas traveling in this body take shelter in dushya and then starts their activity of sammurchana.
The same disease may be produced by different doshas just because they affect a specific site or sthana. Susrutha has given a list of such diseases. In the abdomen doshas produce gulma, cold abscess (vidradhi), udara(including acitis), loss of appetite, distention, cholera (vishuchika), diarrhea (athisara) etc. In basthi (urinary apparatus) they produce prameha, calculi, anuria(muthraghata), painful or burning micturition(muthrakrichra), etc. In rectum and anal canal they cause piles (arsa) and fistula (bhagandara). Similarly they produce hydrocele (vrddhi) in the scrotum, diseases of ear, nose, throat, eyes, brain etc. in the supra cervical region, glands, tumors, enlargement of thyroid (galaganda), cold abscess of lymph glands (apachi) etc. In medo dhathu elephantiasis (slipada), rheumatoid arthritis or gout (vata raktha) etc. in the leg. When doshas take sthana samsraya all over the body, they produce a disease which is manifested on the entire body such as fever, rajayakshma etc.
Just like doshas hethus like krimi, poisons etc. also produce different types of diseases according to the site of sthana samsraya. E.g. Streptococcus haemolyticus produces bacterial endocarditis or pericarditis in the heart, pneumonia in the lungs and meningitis in the meninges.
Sthanasamsraya is the stage in which doshas just start the process of sammurchana. In this condition certain symptoms are produced, they are purvarupas. The specific nature of purvarupa is mainly due to the sthana and not due to doshas. But when dosha dushya sammurchana is completed the disease manifests itself in its full form and in this stage it exhibits the sighns and symptoms specific to the particular dosha as well as to the disease proper. They are called rupas.