Hethu is also known as causative factors that are responsible for the disease causing pathologies. Internal or Nija, and External or Agantu are the two types of hetu. The balance of the three doshas like Vata, Pitta and Kapha can be disturbed by the hetus. Moreover, hetu is classified into factors:
Close factor: This factor provokes or encourages the disease by affecting the equilibrium of three doshas in three stages of day, night, and digestion.
Distant factor: This can affect the equilibrium of the doshas but cannot develop the disease; however, the disease can be developed by other factors.
Weak factor: Can affect the equilibrium, but can’t develop the disease.
String factor: The strength in it causes disease or death after disturbing the equilibrium of the doshas.
Asatmiya Indriyartha Sanjog: Improper use of gyanindriya and karmindriya would lead to disease.
– Atiyog (overuse): When you overuse any sense organs, it would lead to disease related to that organ. Overeating would cause abdominal problems.
– Hinyog (underuse): When you use any organs less or don’t use them, then you get this problem.
– Mithayog (misuse): When you use any sense organ incorrectly or as per its capacity, the function might be totally damaged.
Pragyaparadh: Using your intellect to do incorrect things in spite of knowing its harmful effects falls under this factor.
– Dhi (Intellectual): Disease that is caused by doing something without the knowledge of it.
– Dhriti (awareness): Disease is caused when we do something even after knowing the harmful effects.
– Smruti (memory): Ailments or diseases due to memory loss.
Parinama (time): These are diseases caused due to the abrupt change in the weather under certain climatic conditions.
– Hinayog: Winters are generally colder; if they are less cold, you may get diseases.
– Mithyayog: Unexpected rain in winters would cause diseases.
– Atiyog: Too much of cold leads to diseases.
Dosha Hetu: Disturbance in the equilibrium of a particular dosha, but doesn’t cause any disease.
Vyadhihetu (diseased factor): You can easily identify the cause of a disease as it would be the direct one.
Ubhayahetu (combined factor): The same factor or cause disturbs the doshas’ equilibrium, and also causes the disease.
Utpadakhetu (Predisposing factor): The equilibrium of the doshas is disturbed, and the disease is also caused; however, the factors causing them are not the same. For example, during winter, you do not get any disease but kapha dosha is disturbed.
Vyanjakhetu (exciting factor): These factors excite the doshas but do not disturb their equilibrium; however, this excitement would certainly be the reason for the disease to be caused. For example, the phlegm in your body comes out in the form of running nose or sneezes.
Bahyahetu (external factor): External factors that are outside the body are responsible for causing the disease. Examples are poisons, unbalanced diet, bacteria or fungi, and so on.
Abhyantarhetu (internal factor): Internal factors inside the body are responsible for causing the disease. For example, the water, indigested food, and so on are responsible for causing disease.