Physiology of Sweating – Sveda and Svedavaha Srotas
Dr. Vandana Verma , Assistant Professor, Department of Kriya Sharira
Faculty of Ayurveda, IMS, BHU, Varanasi
- What is Sveda ?
- Mechanism of Sweat formation and sweating
- Functional regulation of Svedavaha srotas
- Composition of Sveda
- Functions of Sveda
- Effects of Svedavriddhi and Svedakshya
- Conditions of excessive sweating
- Svedavahasrotas dusti causes and lakshan
- Applied aspect of Svedavaha srotas
- Svedan (sudation)
Sweat is considered as a waste product which is formed during the metabolism of Meda dhatu and it is replenished by the Kitta part of Ahara. Aacharya Sharangdhar(pradhan khand 5/16,17) has considered sweat as Updhatu of Meda dhatu.
When the ingested food gets digested it gets divides into nutrient part (sara) as well as waste part(Kitta/Mala). From that kitta part feces and urine is formed and the Saar bhaag nourishes to the seven tissues. In each Dhatuvaha Srotas circulating nutrients undergo into the process of metabolism and nourish the respective tissues. During the transformation of each dhatu i.e. from Rasa to Majja dhatu there is formation of waste product for example Kapha is the waste product of Rasa, Pitta from Rakta, Khamal(ear wax) form Mamsa, sweat is the Mala of Meda dhatu, Kesha & Loma are the Mala of Asthi, unctuousness over skin and eye are the Mala of Majja.
किट्टमन्नस्य विण्मूत्रं, रसस्य तु कफोऽसृजः| पित्तं, मांसस्य खमला, मलः स्वेदस्तु मेदसः|| स्यात्किट्टं केशलोमास्थ्नो, मज्ज्ञः स्नेहोऽक्षिविट्त्वचाम्| (C.Chi. 15/18,19)
कफः पित्तं मलाः खेषु प्रस्वेदो नखरोम च|| स्नेहोऽक्षित्वग्विशामोजो धातूनां क्रमशो मलाः| (A.Hri. Sha.3/63)
Srotas are the channels or pathways meant to carry and transform specific substances in the body and maintain homeostasis of the body. These channel may be either microscopic (suksma) or macroscopic (shoola). Aacharya charak has described 13 types of sthoola Srotas and Svedavaha srotas is also a sthoola srotas. Moola of Svedavaha Srotas is Meda & Lomakoopa. Sweat is produced and carried by Svedavaha Srotas. The sweat gland and sweat carrying duct could be understood as Svedavaha srotas. Two kinds of sweat glands are present in the dermis part of skin, one is eccrine gland and other is apocrine gland. The eccrine gland open directly into the skin through pore called sweat pores, while apocrine gland open via duct into the neck of hair follicle this can be understood as the Lomakoopa. Thus the sweat is coming to the skin through two pathways i.e. direct opening over the skin and other is through the root hairs.
Meda Dhatu this adipose tissue (subcutaneous adipose tissue) which is present all over the body could be considered as the Moola of Svedavaha Srotas. The Moola of any Srotas is basically the organ or part of the body which is related to transformation or transport of some substances. Thus these two glands are related with the transport of sweat and for the formation of sweat. As we know that sweating is an adaptive response of the body in the process of thermoregulation and Meda plays an important role in thermoregulation. Therefore, this could be considered as the Moola of Svedavaha Srotas. Aacharya charak has also described moola may be the site of examination of srotas in the condition of its Srotodusti or pathogenesis. In case of Medodusti excessive sweating is found as characteristics so just by observing the state of sweating in a person functional state of Meda dhatu could be inferred.
स्वेदवहानां स्रोतसां मेदो मूलं लोमकूपाश्च (C.Vi.5/8)
Mechanism of Sweat formation
Aacharya charak has described that Sveda is fraction of Udaka(body water) which comes out through skin pores on exposure to heat. The quantity of Udaka is 10 Anjali praman, and is distributed all over the body; it has different names as per location and function. Here Aacharya Charak is referring to the thermoregulation mechanism. When there is increase in body temperature on exposure to the heat or due to other reasons, the thermoregulatory mechanism operates to maintain the body temperature and sweating is the most important mechanism of body to lower down the temperature. यच्चोष्मणाऽनुबद्धं लोमकूपेभ्यो निष्पतत् स्वेदशब्दमवाप्नोति ( C. Sha. 7/15)
Dhamni (Artery ) network in skin in relation to sweat formation.
Aacharya Shushrut has mentioned about the arterial capillary network in the skin which regulate sweating under the description of Adhoga dhamani and Triyaga dhamani. He has described three types of Dhamni, on the basis of their distribution, direction of arrangement in the body and their position. Urdva Dhamni is of 30 types, present above the umbilicus and supplies to the trunk part, upper limb, neck and head.
Adoga Dhamni: supplies to the pelvic organs and lower limbs, are situated below the umbilicus, they are also of 30 types. Eight kinds of Adhoga Dhamni are related with the the Tiryaka Dhamni and this Tiryaka Dhamni are related with the Sweat formation. These Adhoga Dhamni are also related with the separation of mutra, purisha and sveda.
Tiryaka Dhamni: are of four types and each Dhamni get divided into 100 X 1000 x times. Thus they get divided into smaller and smaller, and make a network in the skin all over the body. This description could be understood as capillary network in skin. These capillaries are porous through which exchange of various substances takes place, so these capillaries are related with the nutrition of the body and are related with the Sweat formation also. The rate of sweat formation depends on the vascularity of the skin. When there is exposure to the heat, blood vessels gets dilated leading to more formation of sweat and when there is exposure to the cold blood vessels get constricted and formation of sweat becomes less.
अधोगमास्तु वक्ष्यामि कर्म चासां यथायथम् || मूत्रपुरीषस्वेदांश्च विवेचयन्ति;—- अष्टावन्यास्तिर्यग्गामिनीनां धमनीनां स्वेदमर्पयन्ति; तास्त्वेतास्त्रिंशत् सविभागा व्याख्याताः | (S.Sha9/6, 7)
तिर्यग्गाणां तु चतसृणां धमनीनामेकैका शतधा सहस्रधा चोत्तरोत्तरं विभज्यन्ते, तास्त्वसङ्ख्येयाः, ताभिरिदं शरीरं गवाक्षितं विबद्धमाततं च, तासां मुखानि रोमकूपप्रतिबद्धानि, यैः स्वेदमभिवहन्ति रसं चाभितर्पयन्त्यन्तर्बहिश्च, (S.Sha9/9)
Functional regulation of Sweat gland
Samana vata and Vyaana vata Regulate the formation and secretion of Sveda. Samana vata resides in Sveda, Ambu and Doshsa vaha Srotas. Thus the Samana vata regulates the functions of Svedavaha Srotas i.e. sweat glands and its ducts.
Aacharya Sushrut has described that Vyana vata regulates the circulation of Rasa into the body and secretion of sweat, and oozing of blood (Rakta) through capillaries. Vyana vata also has functional regulation cardiac activity as well as regulation of diameter of the blood vessels especially the arterioles and capillaries. The sympathetic and autonomic regulation of sweat formation may be understood in the terms of regulation by Samana Vata & Vyana Vata.
स्वेददोषाम्बुवाहीनि स्रोतांसि समधिष्ठितः| अन्तरग्नेश्च पार्श्वस्थः समानोऽग्निबलप्रदः|| (C.Chi.28/8)
कृत्स्नदेहचरो व्यानो रससंवहनोद्यतः || स्वेदासृक्स्रावणश्चापि पञ्चधा चेष्टयत्यपि | (S.Ni.1/17)
Composition of Sweat
Aacharya Chakrapani has explained that the Stanya which is formed as the byproduct of Rasa Dhatu and sweat both have mainly the water in their composition. The primary secretion formed by sweat gland is similar to plasma except, it does not contain proteins. It contains sodium ions, potassium ion, chloride ion, urea and lactic acid. The pH level is 4.5 to 7, mineral composition varies with the individual, their acclimatization to the heat exercise, particular stress source, duration of sweating, the composition of minerals in the body.
Sweat is the dwelling site of Pitta dosha. Pitta dosha and Sveda share the relation of Ashraya and Ashrayee. The sweating is basically regulated by the Pitta Dosha, so the rate of sweating will depend on the functional state of Pitta Dosha.
स्वेदः स्तन्यं चाप्यम्’ इति चक्रः ( Chakrapani commentary on S. Su. 15/8)
नाभिरामाशयः स्वेदो लसीका रुधिरं रसः| दृक् स्पर्शनं च पित्तस्य, नाभिरत्र विशेषतः||(A.Hri.Su.12/2)
तत्रास्थनि स्थितो वायुः, पित्तं तु स्वेदरक्तयोः| श्लेष्मा शेषेषु, तेनैषामाश्रयाश्रयिणां मिथः||
यदेकस्य तदन्यस्य वर्धनक्षपणौषधम्| अस्थिमारुतयोर्नैवं, प्रायो वृद्धिर्हि तर्पणात्||(A.Hri. Su 11/26-27)
Sweating and sweat content differs as per Prakriti
In Pitta prakriti persons more sweating is found than Vata and Kapha Prakriti individuals because of inherent dominance Pitta dosha. Pitta Prakriti individuals are fast metabolizers due to higher activity of CYP2C19 GENE than in other two Prakriti. (https://doi.org/10.1093/ecam/nep206. PMid:20015960. PMCid:PMC3135904.)
द्रवत्वाच्छिथिलमृदुसन्धिमांसाः, प्रभूतसृष्टस्वेदमूत्रपुरीषाश्च I विस्रत्वात् प्रभूतपूतिकक्षास्यशिरःशरीरगन्धाः (C.Vi.8/97
Function of Sweat:
Sweat provides moisture and unctuousness to the skin it is also responsible for maintaining the body hairs over the skin (A.Sam.Su19/4).
The secretion of apocrine gland and sebaceous gland get mixed and appears on the surface of the skin and makes a thin layer over the skin, which makes the skin moist and protects it by different kind of infection. The sweat has three major functions thermoregulation, excretion, and protection. क्लेदत्वक्स्नेहरोमधारणैः स्वेद इति I (A. Sam. Su. 19/4)
Effects of Increased Sweating: Excessive sweat, bad odour in body, itching in skin. स्वेदोऽतिस्वेददौर्गन्ध्यकण्डूः …..I (A.Hri Su. 11/14)
Effects of decreased Sweating: loss of body hair, dryness, cracking of skin, less sensitivity to different kind of touch
स्वेदे रोमच्युतिः स्तब्धरोमता स्फुटनं त्वचः (A.Hri Su. 11/14)
स्वेदक्षये स्तब्धरोमकूपता त्वक्शोषः स्पर्शवैगुण्यं स्वेदनाशश्च; तत्राभ्यङ्गः स्वेदोपयोगश्च || S.Su15/11
Causes of Excessive sweating
Excess sweating if found as characteristics in Medavaha srotodusti and obesity (Atishthulata): Characteristics of Medavaha srotodusti are excessive sweating, unctuousness all over the body, swelling all over the body, excessive thirst.
Characteristics of Obesity: Medavaha sroto dusti, excessive body odour, excessive sweat formation.
मेदोवहे द्वे, तयोर्मूलं कटी वृक्कौ च, तत्र विद्धस्य स्वेदागमनं स्निग्धाङ्गता तालुशोषः स्थूलशोफता पिपासा च; (S.Sha. 9/12)
अतिस्थूलस्य तावदायुषो ह्रासो जवोपरोधः कृच्छ्रव्यवायता दौर्बल्यं दौर्गन्ध्यं स्वेदाबाधः क्षुदतिमात्रं पिपासातियोगश्चेति भवन्त्यष्टौ दोषाः I दौर्गन्ध्यं मेदोदोषान्मेदसः स्वभावात् स्वेदनत्वाच्च(C.Su.21/4)
Chakrapani commmentary मेदोदोषादिति दुष्टं मेदो दुर्गन्धं भवति| स्वभावादिति स्वभावादपि मेद आमगन्धित्वेन दुर्गन्धम्| स्वेदनत्वाच्चेति सति च स्वेदे दुर्गन्धताऽनुभवसिद्धैवेत्यर्थः| श्लेष्मसंसर्गादिभ्यो हेतुभ्यः स्वेदाबाधो ज्ञेयः||
Causes of Vitiation of Svedavaha Srotas: Strenuous exercise, rage, exposure to alternate heat and cold, anger, grief, fear. All these causes are related to altered metabolism and heat production.
व्यायामादतिसन्तापाच्छीतोष्णाक्रमसेवनात् | स्वेदवाहीनि दुष्यन्ति क्रोधशोकभयैस्तथा|| ( C.Vi.5/22)
Applied aspect of Svedavaha Srotas
Swedavaha Srotas has great role in temperature regulation, protection of body as well as excretory function. The physiology of Sweating and role of Swedavaha Srotas in temperature regulation, protection of body as well as excretory function have been well described in Ayurveda. Ayurveda duly recognized the applied aspect of Swedavaha srotas in maintenance of homeostasis of body and in eliminating the mala(toxins), has described Swedana (Sudation) as a therapeutic modality in management of Vataja and Kaphaja disorders and as a Poorva karma.
Svedana( Sudation) is a procedure in which heat stress is induced for sweating by various modalities. The heat stress initiates the thermoregulatory mechanism and produces various hemodynamic changes helps in excretion of metabolic wastes.
Svedan (Sudation) is of two types on the basis of application of external heat to induce sweating
- Niragnisveda : No application of external heat to induce sweating
- Saagnisveda: application of external heat to induce sweating
Niragnisveda: Ten measures for Niragnisveda are exercise, residing in warm house, heavy clothing, hunger, aintake of alchohol, fear, anger, application of Upanaha(poultice), wrestling, exposure to sun. All the above mentioned conditions for Niragni sveda stimulates sympathetic nervous system with release of epinephrine & nor epinephrine that increases BMR which in turn increases heat production) which significantly modulates the core temperature as a response to changing environmental conditions. Thus Niragnisveda (sudation without application of direct heat) modalities refer to adaptive mechanisms of human beings.
व्यायाम उष्णसदनं गुरुप्रावरणं क्षुधा| बहुपानं भयक्रोधावुपनाहाहवातपाः|| स्वेदयन्ति दशैतानि नरमग्निगुणादृते|(C.Su.14/64-65).
Characteristics of vitiation of Swedavaha Srotas: Absence of sweating or excessive sweating, excessive dryness of skin or unctuousness, burning sensation.
प्रदुष्टानां तु खल्वेषामिदं विशेषविज्ञानं भवति; तद्यथा- अस्वेदनमतिस्वेदनं पारुष्यमतिश्लक्ष्णतामङ्गस्य परिदाहं लोमहर्षं च दृष्ट्वा स्वेदवहान्यस्य स्रोतांसि प्रदुष्टानीति विद्यात् (C.Vi. 5/8)
Features of Atisvedan (excess sudation)
Aggravation of pitta, fainting (Murcha), heaviness of the body, pain in joints,thirst, burning sensation in the body, Visphota (Blisters), Bhrama (Giddiness), Klama (tiredness), Vomiting, Trishna (thirst) Raktha dushti lakshana.etc. Measures of greeshma rituchrya have been advised to manage the cases of atisvedan. The characteristics of Atisvedan and its management are similar to heat exhaustion and heat stroke.
पित्तप्रकोपो मूर्च्छा च शरीरसदनं तृषा| दाहः स्वराङ्गदौर्बल्यमतिस्विन्नस्य लक्षणम् ||
उक्तस्तस्याशितीये यो ग्रैष्मिकः सर्वशो विधिः| सोऽतिस्विन्नस्य कर्तव्यो मधुरः स्निग्धशीतलः|| (C.Su.12/14,15)
Assessment: Multiple Choice Questions
Q.1. Moola of Svedavaha Srotas is:
- Meda & lomakoopa
- Meda & jaghana
- Asthi & sandhi
Q.2. Excessive sweating is found ………..
- Pitta dushti
- Both 1&2
Q.3. What is cause of vitiation of Svedavaha Srotas:
Q.4.Which Mahabhoot is dominant in composition of sweat:
Q.5.Which of the following is used as a measure for Niragni Sveda:
- Intake of alcohol
- All of the above
Q.6.Which of the following is not a feature of Atisvedan.
- loss of coldness from body
- Aggravation of Pitta
Q.7.Which Acharya has considered Sveda as Updhatu of Meda Dhatu?
Q.8. What is Pramana of Udaka in body:
- 9 Anjali
- 10 Anjali
- 6 Anjali
- 2 Anjali
Q.9. Which Vata dosha regulates the formation and secretion of sweat:
- Prana vata
- Udana vata
- Vyana vata
Q.10. Which is not a feature of increased Sweating:
- Bad odour
- Cracking of skin
- Excessive sweating
- Itching in skin
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