The fundamentals of the concept of human physiology in Ayurveda are grounded with the concepts of Doshas, Dhatus and Malas. These three are the important substances and necessary elements to maintain hemostasis of the body. The balanced state of these three is
important for various functions, origin, development and progression of life. Doshas are the biological entities which govern and regulate all the physiological functions of the body. Dhaatu are the tissues within the body and Mala are the excretory waste products that are formed during digestion and metabolism processes. Acharya charak has given more importance to the understanding of Mala as it is the factor which produces interference in the normal physiological function of the body and initiates the disease. Mala includes the accumulation of Doshas, Dhaatus or the metabolic waste products which get stuck in the various channels within the body.

The Mala can be classified into two categories:

1.Aahara Mala : It includes Mutra (urine), Sweda (sweat) and Purisha (feces).

2.Dhatu Mala : It includes Kapha, Pitta, Khamala, Sweda, Keshaloma, Sneha and Rasa.

Amongst all, Sweda is transported via Sweda Vaha Srotas and excretes the waste products formed during metabolic and digestive process. It also regulates the temperature of the body along with the Pitta Dosha. It is the fraction of Udaka i.e. water that comes out via skin pores and hair follicles. It is the waste from both Aahara and Medha Dhatu.

Sweda is produced from Udaka and comes out from Moola of Swedavaha Srotas and later combines with Ushma i.e heat. When the body is exposed to heat, in adaptive response the person starts sweating to lower down body temperature. Sweat is related with Pitta dosha and is one of the important sites of Pitta Dosha along with Rakta Dhatu i.e. blood. Pitta dosha is responsible for all the metabolic processes in the body which results in evolution of heat. The body heat thus, depends on Pitta dosha and its functional state. During the process of sweating there is an exothermic process in which the heat is lost along with sweat because of its relationship with Pitta dosha. Thus, the temperature of the body is regulated with the help of sweat and Pitta dosha. This process of secretion of sweat and it’s expulsion is regulated by Samana and Vyana Vata. Furthermore the quantity of sweat secreted and excreted is dependent upon the level of hydration and metabolism of the body. The loss of sweat is an important mechanism for the maintenance of body temperature. Sweat regulates the body temperature, cools the body, purifies the blood, etc.

Triyaga Dhamani is the concept that describes arterial and venous network of the skin in relation to the sweat formation. Each of the four blood vessels is divided into hundreds and thousands of branches and finally become innumerable so that every part of the body is
covered by them in a form of network and their networks open in hair follicles and skin. From these openings the sweat is let out of the body. These openings are also responsible for the perception of sensation of touch. Sushruta says that rakta dhatu is responsible for these sensations along with the simulations caused due to vata dosha.

During the winter season the exposure of cold leads to closure of body pores and prevents external heat loss and causes increase in metabolic process, heat production and vasoconstriction in skin vascular bed. This in ayurvedic text is known as vata vriddhi.

Factors affecting sweat and thermoregulation of body are:

1.Prakriti- Psychosomatic constitution: The quantity and the odour of the sweat may be different for different individuals as the composition of Mala of Medha dhaatu is different for different individuals. The Pitta dominated individuals have a foul smell of sweat due to more dravya, ushna and vishra properties of Pitta dosha. The quantity of sweat depends upon the hydration level of the body as well as the water intake of the individual. For the regulation of temperature of the body, the level of hydration is necessary. Further the pitta dominated individuals result in more sweating and water loss due to production of more heat and the water intake of the individuals is more.

2.Emotional states and mental health:
The negative emotional states like fear, anger or grief leads to higher sympathetic activity due to aggregation of Vata and Pitta dosha which in turn results in more sweating. Due to this negative emotions and aggravation of vata dosha there is an increase in Pitta Dosha as well. As Pitta Dosha increases the heat in the body increases and thus the rate of sweating also increases.

3.Level of exercise:
During exercise the Agni is enhanced which results in increase in metabolic activity and heat production which in turn leads to sweating in order to maintain temperature of the body.

4.Ati Sthaulya – Obesity:
Obesity is due to Medovriddhi, and excessive formation of sweat takes place. This is because vit is the mala of Medha dhaatu. Obesity is also associated with excessive heat loss due to excess deposition of fat in the subcutaneous layer resulting in thickness of subcutaneous tissue and vasoconstriction in the skin because of sympathetic overactivity due to autonomic dysregulation. According to Ayurveda obesity leads to vata vriddhi and srotavrodha due to over accumulation of fat which results in augmentation of digestive fire, more intake of food and thus, increased information of ahara Mala i.e sweat also.

When the sweating is vitiated, it leads to skin disorders, gout and febrile state of malaria and typhoid, and obesity. These are counted under the causes of secondary hyperhidrosis. These conditions are managed by the same treatment as that for the fever. Further oil bath, sudation and physical exercise are recommended in case of vitiated sweating.

Thus, Ayurveda provides a good knowledge with regards to thermal regulation by the means of sweating of the body. Ayurveda duly promotes the maintenance of hemostasis of the body and elimination of toxins which are necessary to adopt in swedana chikitsa. Heat applied during this treatment produces heat stress and initiates thermoregulatory mechanisms which produce various hemodynamic changes, which help in excretion of metabolic waste and enhance immune mechanisms. Hence sweating has a great role in regulation of body temperature, protection of body and excretory function.