Sweda

The term sweda means sweat or perspiration. It is one among three metabolic excretory products (mala) like urine (mutra) and stools (purisha). These are also known as dushya (which get vitiated). [A.Hr.Sutra Sthana 1/13] Excretory products (mala) are important in human physiology. They are formed in routine physiological and metabolic activities in the body. It is important to cleanse or purify body by removing the wastes. If accumulated, the mala have ability to pollute dosha and dhatu of the body.

Perspiration or sweating (sweda) is important for removing wastes formed in skin and maintain body temperature i.e. thermoregulation. Sweda is basically the end product of meda dhatu metabolism. This article describes concept and applications of sweda in Ayurveda and contemporary sciences.

Sweda

Section/Chapter/topic	Concepts & Practices / Sweda
Authors	Bhojani M.K.1, Durga Rani1, Jogalekar A.A.2
Reviewers	Basisht G.3, Khandel S.K.4
Editor	Deole Y.S.5
Affiliations	1 Department of Kriya Sharira, A.I.I.A., New Delhi, India 2Department of Samhita-Siddhanta, A.I.I.A., New Delhi, India 3 Rheumatologist, Orlando, Florida, U.S.A. 4Arogyalaxmi Ayurveda Consultancy, Jaipur, India 5 Department of Kayachikitsa, G.J.Patel Institute of Ayurvedic Studies and Research, New Vallabhvidya Nagar, Anand, Gujarat, India
Correspondence email	meera.samhita@aiia.gov.in, carakasamhita@gmail.com
Publisher	Charak Samhita Research, Training and Development Centre, I.T.R.A., Jamnagar, India
Date of first publication:	July 31, 2022
DOI	In process

Derivation & definition

Literal meaning of sweda is to cook or to steam. It is the perspiration produced due to exercise or heat. The word sweda is derived from the verb ‘svid’ meaning exudate or perspiration from the body parts as a result of gharma or heat. [Vachaspatyam] The terms like sweating, sweat, perspiration, warmth, vapor, steam etc. [Monniere Williams dictionary]

Sweda is a part of water or watery exudate within the entire body excreted through the hair pockets (lomakupa).[Cha.Sa.Sharira Sthana7/15), [Arunadatta on A.Hr.Sharira Sthana 3/36]

It is closely regulated by heat in the body (ushma). Sweda is formed during the metabolism of meda dhatu and as part of water/fluid component (udaka) in the body. [Chakrapani on Cha.Sa.Chikitsa Sthana 15/18-19]

In contemporary medical dictionaries, the literal meaning of the word ‘sweat’ is perspire or exudation or moisture from the sweat pores.

Synonyms

Gharma (Shabdakalpadruma) , nidagha, seka, medomala [Hemadri on A.Hr.Sutra Sthana 1/13]

Panchabhautika constitution

Sweda has dominance of jala and teja mahabhuta. Some scholars consider it as jala mahabhuta dominant.[Chakrapani on Su.Sa.Sutra Sthana 15/7] It is listed among the watery components in body. [Cha.Sa.Sharira Sthana 7/16] [A.Hr.Sharira Sthana 3/4]

Physiology of formation and excretion

Sweda is produced as byproduct in metabolism of meda dhatu [Cha.Sa.Chikitsa Sthana 15/18], in channels of transformation and transportation of meda dhatu (medovaha srotasa).[Chakrapani on Cha.Sa.Sutra Sthana 28/4] Sweda bestows moistness and softness of the skin. It is a part of waste part (kitta bhaga) of the metabolized food. [Cha.Sa.Sutra Sthana 28/4]

Sweda or sweat is basically the fluid element excreted through sweat pores due to heat or activity along with dissolved minerals and solids. Its formation is regulated by means of external temperature, fomentation or heat treatments. The main seat of channels of formation and transportation of sweat (swedavaha srotas) are meda dhatu and the small pores on the skin (romakoopa). It depends on excess heat in body. [Cha.Sa.Sharira Sthana 7/14]

Quantity of sweda (sweda anjali pramana)

The average amount of sweda in the entire body is ten anjali. [Cha.Sa.Sharira Sthana 7/15] [A.Hr.Sharira Sthana 3/80] It varies according to heat and humidity level in the surrounding atmosphere. However, due to individual variability, the amount may be variable and cannot be determined.[Su.Sa.Sutra Sthana 15/17]

Physical properties

It is watery, slightly unctuous and has a yellowish tinge and odor. Sometimes, it may be in vapors state.

Regulation of sweat secretion:

Vyana vayu helps in the excretion of sweat from the body. Conduction of sweat from the root of the hair, opening of the skin pores and help in the excretion of sweat, all these functions belong to vyana vayu. [A.Sa.Sutra Sthana 20/6]

Functions of sweda

Sweda controls body temperature by way of expelling excess water and toxins, cools the body, moistens skin & hair and carries excess fat from the body and purification of the blood. Maintaining moisture (kledavidhruti) is the main function. [A.Hr.Sutra Sthana 11/4] Proper functioning of hair follicles (kesha vidhruti or roma-avlambana) is added. [Arunadatta on A.Hr.Sutra Sthana 11/4]. Moistness of skin (kleda or kledana) and softness of skin (twak saukumarya) are the main functions of sweda. [Su.Sa.Sutra Sthana 15/4]

• It keeps the skin and hair moist, delicate, smooth & maintain the integrity of skin.
• It helps to maintain water balance in the body.
• It helps in maintenance of body temperature
• It prevents different vatika disorders
• It also excretes the various kind of toxins from the body

Swedavaha srotas

The sites of origin of channels carrying sweda (swedavaha strotas) are adipose tissue (meda dhatu) and hair follicles (romakoopa). This is reflected in the characteristics of vitiation of medavaha srotasa like absence of perspiration, excessive perspiration, roughness or excessive smoothness of the body, generalized burning sensation, and horripilation.[Cha.Sa.Vimana Sthana 5/8] Sweda is carried and excreted through eight obliquely spread vessels (tiryakadhamani).[Su.Sa.Sharira Sthana 9/8]

Causes of vitiation (swedavahasrotodushtinidana):

These channels get vitiated due to excessive exercise, exposure to excess heat, indulgence in heat and cold things without following the prescribed order, anger, grief and fear.[Cha.Sa.Vimana Sthana 5/22]

Symptoms of excessive sweating (swedavriddhilakshana/atiswedalakshana):

1. Foul smell or excessive body odour (daurgandhya)
2. Itching (kandu)
3. Excess sweating (atisweda)

[Su.Sa.Sutra Sthana.15/15] [A.Hr.Sutra Sthana 11/14]

Symptoms of reduced sweating (swedakshayalakshana):

1. Contracted sweat gland and ducts, stiffness and obstruction of hair follicles (stabdharomakoopta)
2. Dryness of skin, cracking of skin (twak paripatana) and skin disorders (twak dosha)
3. Altered tactile sensation (sparshavaigunya)
4. Lack of sweat or absent sweat (swedanasha)
5. Scaling of skin (twaksphootana)
6. Falling of body hair (romachyuti)

[A.Hr.Sutra Sthana 11/22], [Su.Sa.Sutra Sthana 15/15], [A.Sa.Sutra Sthana 19/11]

Treatment:

In the above conditions, oil bath and oil massage (abhyanga) and fomentation (swedana) are the methods of treatment.

Sweda and pitta prakriti:

Excess sweating (swedaadhikya)is a characteristic of pitta prakriti individual. [Su.Sa.Sharira Sthana 4/68]

Sweda and pitta dosha relationship:

There is a close or concomitant relation between pitta dosha and sweda. [A.Hr.Sutra Sthana 11/26-29] This indicates the anatomical and physiological relation between two components. These possess similar causes of vitiation, similar line of management, similar pattern of disease affliction. Thus, the line of management of pitta ailments is in concordance with the management of sweda related disorders. As both the entities i.e. sweda and pitta are related with the component of heat in the body (ushma), these are related closely like pitta dosha takes abode of sweda (ashraya- ashrayisambandha).

Physiology of sweat

Sweat is a clear, watery and salty liquid produced by the sweat glands present in the skin. Sweat is mainly produced in noticeable amounts under the arm, feet and palms. When it comes in contact with the bacteria on skin, it can cause a smell. Regular bathing and use of antiperspirants or deodorant can help to control odor. In extreme conditions or during heavy exercise, large quantities of sweat is produced. It proves to be a great method of thermoregulation as long as humidity in surrounding atmosphere is relatively low. Stimulation of anterior hypothalamus-preoptic area is responsible for the action of sweating. The impulses from this area are transmitted in the autonomic pathways to the cord and then through the sympathetic outflow to the skin and elsewhere in the body.[Text book of physiology.p.298] The volume of sweat produced and expelled every day is generally about 100ml/day and may vary from person to person. The water loss through sweat may increase upto 1-2 L/hour in case of exercise or extremely hot weather.[Text book of physiology.p.915-16]

Sweat glands:

Sweat glands are of two types:

1. Eccrine glands
2. Apocrine glands

Eccrine glands: These are the common sweat glands distributed all over the body, especially over the thick skin. The eccrine sweat gland is basically of tubular structure which at beginning is in the deeper part of dermis and is highly coiled. The rest of the gland courses through the dermis- epidermis- open to the exterior. Sweat forms by coiled portion. These are functional throughout the life. These are present largely over the back and chest regions. [Hutchinson’s Clinical Methods.p.512]

When synthesized the sweat is isotonic, but while moving towards the exterior, some sodium ions are reabsorbed. In case of severe sweating, this reabsorption is more intense due to the action of aldosterone. The thermoregulation via sweating occurs through the eccrine glands innervated by sympathetic cholinergic fibres. The eccrine sweat is basically made up of water and sodium chloride (NACl). It may also contain mixture of many other chemicals from the interstitial fluid as well. The amount of sodium and cholride in the eccrine sweat is considered to be less, 60mmol/L and 70 mmol/L respectively.

Apocrine glands: These glands are located deep in subcutaneous layer in limited areas like axilla (armpit), pubic region, around the nipple of breast, scalp. The activity of apocrine glands increases with the onset of puberty and declines at old age. This process shows that these glands have got some relationship with reproductive physiology. The secretion from apocrine glands is odorless but bacterial decomposition makes it odorous, secretion show cyclic changes in females with menstrual cycle. These glands are structurally similar to eccrine glands, but are larger. Their coiled region lies within the subcutaneous tissue rather than the dermis. In contrast to the eccrine glands, apocrine glands produce vicious, lipid rich sweat comprising of proteins, sugars and ammonia.

The third type of glands i.e. apoeccrine glands have been described by Sato et. al in 1987. These are intermediate in size and develop from both eccrine and apocrine glands. These are mainly located in the axillary part and don’t play a significant role in thermoregulation.

Mechanism of secretion of sweat:

Though the eccrine glands are supplied by symphathetic fibres, yet adrenaline (epinephrine) has got little or no action on them. The apocrine however responds to both adrenergic and cholinergic stimuli. Pilocarpine, which stimulates the parasympathetic fibers, increases the flow of sweat and atropine which paralyses the parasympathetic endings, abolishes sweating.

Different types of sweating:

1. Insensible sweating: which occurs even in cold climate amounts to 600 – 800 ml daily.
2. Thermal sweating: This occurs in hot environmental temperature, the threshold being 28°C for men and 31˚C for women. As the environmental temperature rises sweating increases. It is to be emphasized that when the ambient temperature is higher than body temperature sweating is the only method of keeping the body temperature normal.
3. Psychic sweating:-

Emotional sweating: In emotional condition, sweating occurs chiefly in the palms, soles, and axilla and upto some extent it is also present at head, neck and elsewhere in the body.

In muscular exercise: The sweating i.e. both thermal and mental is reduced by cold, which at the same time also reduces, cutaneous circulation. It is also reduced by dehydration which be the result of deprivation of fluids intake or due to the process of sweating itself.

Hot & spicy food intake: Eating of spicy food stimulates sweating (gustatory sweating), because pain in nerve endings in the mouth are stimulated. Hence reflect sweating in forehead neck and face.

Composition of sweat:

Sweat mainly consists of secretions of the eccrine glands. It is the most dilute amongst all the animal fluids. When freshly collected, it contains epithelial cells and some sebum. When filtered, it forms a clear colorless fluid. The human sweat has specific gravity of about 1.001-1.006 and a pH of 3.8 to 6.5.

Table 1: Composition of sweat

Each 100 ml of sweat contains
Water	99.22- 99.74g
Solids	1.174- 1.587g
Ash	0.144- 0.566g
Creatinine	0.1-1.3mg
Urea	12-57 mg
Lactic acid	285-336 mg
Carbolic acid	2.8 mg
Sugar (as glucose)	1-3 mg
Uric acid	0.07-0.25 mg
Ascorbic acid(as a dehydroascorbic acid)	70.5µg
Total nitrogen	33.2mg
Non protein nitrogen	27-64 mg
Amino acid N	1.1- 10.2mg
Ammonia N	5.9 mg
Urea N	5-36 mg
Calcium	1-8 mg
Iodine	0.5-1.2 ug
Iron	0.022-0.045
Chloride	36-468 mg
Na+	24-312mg
K+	21-126mg
Sulphur	0.7-7.4 mg
Cooper	0.006mg
Amino acids	43.62 mg

Role of Swedana as therapy

In Ayurveda, the treatment “Swedanakarma”, is a therapy by which person is made to sweat. Swedana (sweating or fomentation) is used for all vata and kapha dominant diseases. [Cha.Sa.Sutra Sthana 14/3] If administered after oleation, fomentation controls vata and thereby facilitates the elimination of feces, urine and semen. [Cha.Sa.Sutra Sthana 14/4]

Even dry pieces of wood can be bent by means of oleation and fomentation, when duly applied. This simile shows immense benefit of swedana.

Types of swedana:

A. Agni sweda: It is swedana or fomentation involving the application of direct heat. They are of 13 types where the heat is produced from fire.

B. Anagni sweda: This swedana or fomentation is done without the application of direct heat. The ten methods which in a way serve the purpose or fomentation without involving the direct application of heat, are exercise, residing in a warm chamber, wearing of heavy clothing, hunger, excessive drinking, fear, anger application of poultice, wrestling and exposure to sunshine. Perspiration is indicative of the exercise being performed correctly.

Indications:

Fomentation is useful for coryza (pratisyaya), cough, hiccup, dyspnea, heaviness of the body, pan in the ear, neck and head, hoarseness of voice, spasmodic obstruction in the throat, paralysis of the face, one limb, whole body or half of the body, in flexures of the body, distension of the abdomen, constipation and suppression of urine, pandiculation (vijrmbhaka), stiffness of sides of back etc.

Contraindications:

The physician should not administer fomentation therapy to those who have taken too much astringents and alcohol, the pregnant woman, those suffering from bleeding disorders (raktapitta), diarrhoea, paittika type of obstinate urinary disorder specially diabetes mellitus, inflammation and prolapse of the rectum (vidagdha- bhrashta-bradhna), toxic conditions, alcoholism. Those having pitta dominant constitution and dry skin, fatigue, unconscious, fatty, thirsty, hungry, in a fit of anger and anxiety, those suffering from jaundice, abdominal disease, gouty arthritis (vatarakta), loss of vision (timira), those who are weak and dried up and who’s ojas has been reduced.

Importance of concept of sweda in prevention of diseases

The daily regime involves many measures to arrest the impaired hygiene conditions related to sweda. The daily regime interventions like bath (snana) [Cha.Sa.Sutra Sthana 5/93], cleaning body (shariraparimarjana) [Cha.Sa.Sutra Sthana 5/94] are directed towards removal of odour and loathsomeness due the sweda. The appearance of sweda or swedagama is also an indication to stop exercise denoting it as an important aspect of physical endurance or stress.[Cha.Sa.Sutra Sthana 7/33]

“Sweda” as an important entity in diagnosis of diseases

Sweda is an important diagnostic indicator of impaired fat metabolism (meda dhatu agni) and body temperature. Excess sweating (atiswedana) is a feature of morbid obesity (atisthoulya). [Cha.Sa.Sutra Sthana 21/4] It is a feature of jwara [Cha.Sa.Chikitsa Sthana 3/132], udara roga. [Cha.Sa.Chikitsa Sthana13/20] Excess sweating is present as clinical sign of kushtha [Cha.Sa.Chikitsa Sthana 7/11], pittaja pandu [Cha.Sa.Chikitsa Sthana 16/21], tamaka shwasa [Cha.Sa.Chikitsa Sthana 17/64], vatarakta. [Cha.Sa.Chikitsa Sthana 29/16] Lack of sweating is present in conditions like eka-kushtha [Cha.Sa.Chikitsa Sthana 7/21], vatarakta. [Cha.Sa.Chikitsa Sthana 29/16] Sweating is a prodromal sign of prameha [Cha.Sa.Chikitsa Sthana 6/13] and kushtha. [Cha.Sa.Chikitsa Sthana 7/11]

According to the contemporary medical sciences as well, the increased sweating or hyperhidrosis may be a constitutional abnormality often present with family history. It can also be physiologically present as feature of flushing at the time of onset of natural menopause. Pathological causes might include thyroid over-activity, phaeochromocytoma, acromegaly, gustatory hyperhidrosis (autonomic dysfunction and diabetes mellitus), serotonin secreting carcinoid tumors of gut. It is also seen in the patients with acute hematological malignancies. [Hutchinson’s Clinical Methods.p.268]

Therapeutic aspects related to the concept of sweda

The treatment of swedavahastrotodushti is based on the management of fever (jwara vyadhi) (Cha.Sa.Vimana Sthana 5/28], (udara vyadhi). [Cha.Sa.Chikitsa Sthana 13/20]

Recent advances in assessment of sweat

The assessment of amount and composition of sweat is important in the conditions like cystic fibrosis. The sweat test mentioned in this condition is a three steps procedure including sweat gland stimulation, sweat collection and chloride measurement. Iontophoresis of pilocarpine is the most commonly performed procedure for the same. The laboratories collect sweat onto gauze, filter paper, or into macroduct coils and measure the activity of 1 or more of the following characteristics like chloride level, conductivity, sodium level, and/or osmolality present in the sample. Different biomarkers present in the sweat are important in the diagnosis of lifestyle disorders like diabetes, cancer as well. It is a biofluid, hence can also help to determine the human microflora. It can also help in assessment of drug, ethanol level, metals and non-metal levels in the body thus having a wide application in the field of proteomics, metabolomics, genomics etc.

Articles referred

1. Aneesh T et.al. explained the scientific reason of exclusion of the sweda from the list of natural urges and physiology of sweda or perspiration in detail.
2. Shweta V et.al. stated the inter-relationship between meda dhatu and sweda along with the modern co-relation of adipose tissue and sweat.
3. Shraddha C. and Anjana G. have elaborated the diagnostic importance of sweda with respect to different pathological and physiological conditions.
4. Pretty P. has elaborated the concept of sweda in the purview of dhatumala.

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Deerghanjiviteeya Adhyaya, Vividhashitapitiya Adhyaya, Sroto Vimana, Sharira Sankhya Sharira

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