Diseases, according to Ayurveda are caused by the imbalance in the three doshas. The predominance of a dosha in an individual's constitution often indicates his or her vulnerability to a particular disease. Diseases in Ayurveda are classified according to thee origin of their causes. Diseases which originate from factors within the human body, including psychosomatic diseases, are called adhyatmika. Adhyatmika diseases are further divided into hereditary diseases, congenital diseases and those caused by the aggravation of the doshas. Adhibhautika diseases are those whose origin can be traced to external physical factors such as germs and accidents. Adhidaiveka diseases are caused by the seasons, planetary influential, providential causes and so forth. The physician diagnoses a disease in an individual by an examination of the patient based on three general methods. These methods are common to understanding any phenomenon in the universe.  

Direct observation or pratyaksha: This is done through the senses: seeing, hearing, smelling, touching and tasting. A direct contact between the senses and the object of examination is thus established.      

Inference or anumana: Just as one deduces that there is a fire when one sees smoke, one can make deductions in the observation of certain substances under the microscope. For instance, the examination of stool under a microscope will give clues about the state of the health of a person.    

Authoritative statement or shabda: Experts have bequeathed to us a legacy of authoritative statements regarding diseases. The patient is interrogated closely to determine the exact nature of the diseases. The client's relatives too are questioned for in this way the client?s previous history of diseases can be recorded. Fortified with the knowledge from previously recorded cases and the findings of experts, the physician can make a dosha determination.

Following these three principles, a brief examination of the patient proceeds in three stages: visual observation or darshana, touch or sparshana, interrogation or prashna. Another tool of dosha determination in Ayurveda involves the eight-fold method of examination or ashtasthana pariksha which has the following steps:          

1. Examination of the pulse or nadi pariksha: Pulse examination is carried out with the help of radial artery. The index, middle and ring fingers of the right hand are used in pulse examination. The index figure is placed about the width of the client?s wrist below root of the thumb, the other two fingers are placed next to the index.
            Certain rules have to be observed in pulse examination.    
                                                   

(a) The examination should be carried out preferably in the morning after ablutions, on an empty stomach. The pulse should not be examined immediately after a bath, or oil massage, nor when the patient is hungry or thirsty. The examination can also be carried out in the afternoon only if the patient has not eaten for three hours. [ed note: some authorities say, before 10 am pulse tells prakriti and after 10 am one learns vikriti pulse only; others say deep pulse still tells prakriti after 10 am]           
                                                       

(b) The pulse on the right hand of men and the left hand of women must be examined. 
 

(c)The doctor has to have total concentration.      

(d) The examination of the pulse is at least repeated three times. Each time the pulse is gently and evenly pressed, then the pressure is released. It is important that the doctor feels the pulse of the patient and not the capillaries of his own fingers.     

If all three doshas are aggravated (the state of sannipata), the pulse movement resembles that of a woodpecker. A healthy person's pulse is slow steady and regular. A regular pulse beat of thirty times always indicates good prognosis. While examining the pulse some other factors must also be taken into consideration: vayu content in the body increases in the old stage, in the late afternoon, late at night, two hours after eating, during summer or in the beginning of the rainy season. Pitta content goes up during youth and middle age, at noon, at midnight, while digesting food and in autumn and the amount of kapha is more in the morning, in the evening, immediately after eating and in spring. Children have more kapha in their bodies. During pregnancy, which is a bi-cardiac stage,        

2. Examination of physical features: Vayu-dominated patients normally have a rather dry and cracked skin and dry hair. They do not like cold things. Pitta-dominated patients are frequently thirsty and hungry. Their skin is hot to touch and often yellowish. The palms and soles are frequently coppery in colour. They have somewhat less hair. Kapha-dominated patients have compact joints, bones and muscles. They are never excessively thirsty or hungry.   

3. Examination of the eyes: In case of Vayu diseases, the patient will complain of a burning sensation in the eyes. The eyes will also be dry and smoky. Pitta type of diseases will manifest in a yellowish tinge in the whites of the eyes, an aversion to light and a burning sensation. Unctuous and dull eyes and Kapha predominance.          

4. Examination of the tongue: Vayu aggravation is indicated when the tongue is cold, rough and cracked. A red or bluish tinge indicates Pitta aggravation. And a white and slimy tongue indicates Kapha aggravation. The tongue is dark with eruptions when all the doshas are aggravated.        

5. Examination of the skin: A cold skin indicates Vayu aggravation. When the skin is hot to touch, Pitta is aggravated and a moist and wet skin indicates Kapha aggravation.

6. Examination if nails: Cracked and dry nails indicate Vayu aggravation, while red or yellowish nails indicate Pitta aggravation.           

7. Urine examination  

8. Stool examination  

Applying these methods of examination, an experienced physician is able to comprehend a general impression about the client?s individual constitution and which dosha or combination of doshas is affected. The therapy can thus be broadly identified.

Ayurveda looks for food and herbs as having similar effects on the human body. Food and herbs are composed of the same five elements that are found in nature. Therefore, the components of both can be categorized to these five elements. Thus, even if these herbs are continued after the body has regained its normal state, they can provide immunity against disease by strengthening the system in much the same way as a tonic does.