In naturopathy, treatment is applied on skin and the application medium is water because water can absorbs greater quantity of heat then airs and is also rich in oxygen.

Effect of cold and hot:
1. Regularization of cellular metabolism in naturopathy by Cold Therapy and Hot Therapy
2. Excretion of waste material by cold therapy and hot therapy in naturopathy

When cold application is applied on particular part of body or whole body surface, temperature decreases, resulting in excitement of cold receptors and free nerve endings beneath the skin.
• They carries signal through nerve fibres to stimulate the sympathetic centers of posterior hypothalamus. Stimulation of posterior hypothalamus results in constriction of capillaries and arteriovenous anastomosis. Skin vasoconstriction occurs
Simultaneously as surface temperature decreases core temperature tries to maintain body temperature constant. In order to control the vasoconstriction primary motor center of posterior hypothalamus is activated. This center than transmits signals through bilateral tracts down the brain stem in to the spinal cord and finally, to anterior motor neurons of the site. These signals increase the muscle activity throughout the body
• Heat production by metabolic system is increased by
a) Shivering occurs when muscle tone (activity) rises above certain level trying to return back the temperature normal. Shivering increases heat production in body.
b) Norepinephrine and epinephrine in blood secreted by sympathetic stimulation causes immediate increase in rate of cellular metabolism. This effect is called chemical thermogenesis.
c) Preoptic area of hypothalamus on cooling increases the production of neurosecretory hormone, thyrotropin-releasing hormone. This in turn stimulate the secretion of thyroid stimulating hormone in anterior pituitary gland. Due to this thyroxin is stimulated. Increase of circulating thyroxin increases rate of cellular metabolism i.e. chemical theromogensis. The another mechanism of chemical thermogenesis is carried by secretion of thyroxin

Chart of cold therapy

Hot application over particular parts of body or whole body for appropriate time increase the surface temperature of body. (Excess exposure to heat or high temperature many cause hyperthermias). Increase in surface temperature stimulates warmth receptors. Signals are carried through nerve fibres to sympathetic centers of posterior hypothalamus. This inhibit posterior hypothalamus. Inhibition of posterior hypothalamus causes vasodilatation. As surface temperature increases above certain point, core temperature gets effected.
Effects of Vasodilatation :
• Improves blood flow which -
Provides local warmth thus helps in tissue metabolism.
Increase nutrients
Removes waste products
Decreases venous congestion
• Reduces blood viscosity, improves the delivery of leukocytes.
• Lymphatic circulation increases due to increase in permeability of capillary, which helps in removal of waste product and increased nutrient to cell.

On the other hand core temperature effected. In order to maintain body temperature constant, preoptic area of anterior hypothalamus excited and passes the impulse of sweating to cord through autonomic pathways and then through sympathetic nerves to skin.
Sweating is the process of removing excess heat from body. Sodium and chloride ions are lost in profuse sweating. During this process precursor fluid is secreted. They pass through duct slowly so sodium and chloride ions are reabsorbed and there concentration falls to low. This fall, in concentration of ions reduces the osmotic pressure of fluid to such a level that water is also reabsorbed.
Decrease concentration of sodium and chloride ions allows progressively better conservation of salts. Aldosterone is secreted as a result of decrease concentration of sodium and chloride ions, which helps in better conservation of salts. This process helps in maintenance of electrolyte concentration.
Thus it helps in thermoregulation, it also helps in excretion of some salts like ammonia and by products

Chart of hot therapy

Note: - After Hot therapy, whole body cold bath is essential to attain maximum effect.

Excretion of waste material by cold therapy and hot therapy in naturopathy:

As cellular metabolism increases, some toxins are generated. Excretion mostly is done by kidney while excess protein and some of these toxins are return to circulation by lymphatic.
Kidney maintains the three homeostatic functions which includes
1. Excretion of unwanted and potentially toxic products of tissue metabolism.
2. Regulates body fluids and electrolyte in circulating volume by excretion or conservation of water and solutes.

These functions of kidney are carrying out by ultrafilteration of plasma, selective absorption and tubular secretion of solutes by the process of osmosis and diffusion. Changes in temperature regularize the factors, which helps in these processes.
Hot and cold therapy helps in regulation of these processes.

As cold is applied we see, that muscle activity increases and rate of circulation also increases. Increase in muscular activity and circulation causes intrinsic pumping of lymph vessels.
By applying mechanical methods (nonthermal methods) i.e. by compression of tissues by objects outside the body gently causes extrinsic pumping of lymph vessels.
Every time, by intrinsic or extrinsic pumping, interstitial fluid pressure rises temporarily to a positive value. This causes minute amount of fluid to move in to lymphatic and subsequently to be pumped away from tissues. The recoiling capability of elastic structure in tissues creates suction in tissues spaces.
Thus negative pressure is always maintained.
Thermoregulation helps in elevating the factors responsible for increasing interstitial pressure to a certain point. It tends to increase lymphatic pressure, which increases the rate of lymph flow.
Thus excess protein is returned back to circulatory system and normal rhythm of lymphatic system is maintained.

All these are active principles behind Hip bath, Mud pack, Mud bath, Whole body hot bath/cold bath ,Cold sheet wrapping, Spinal pressure bath, Chlorophyll bath, Sunbath, Saunabath, Steambath, Hot foot bath/cold foot bath, Hot and cold affusion.

Skin, urinary tract, lungs, and distal part of colon and rectum are excretory organ. After digestion in small intestine, absorption of water and electrolyte from chyme takes place in proximal half of colon. The storage of faecal matter has done in distal half of colon. When the mass movement forces faeces in to rectum, the desire for defecation is normally initiated.
Faecal matter is composed of normally ¾^th water and ¼^th solid matter composed of dead bacteria, fat, inorganic matter, protein, undigested roughage.

Anatomically the mucosa of large intestine is lined with Crypts of Lieberkuhn but villi are absent.
Epithelial cells of large intestine do not secrete enzymes. Surface epithelial of large intestine contains large number of mucous cells dispersed among other epithelial cells, which secrete only mucous. Large amount of mucous is secreted. Active transport of bicarbonate ions takes place by epithelial cells. The bicarbonate ions are present in large quantity in this mucous.
Mucous in large intestine protects the wall against excoriation and from bacterial activity that takes place inside the faeces, also provides the adherent medium for holding faecal matter together. Bicarbonate ions in mucous maintains the alkalinity of secretion i.e. pH.

Normally the movement of colon is sluggish. Unhealthy life style or habits of neglecting the normal calls of defecation often leads to availability of faecal matter storage for a long time for absorption of fluid. This thing associated with large quantities of dry hard faeces in descending colon.

When the dry hard faeces is stored in distal part of colon for long time, the chyme that enters in proximal part of colon is also available for long time. Availability of faecal matter for long time results in increased absorption of fluid, Ca⁺⁺, Cl^- and Na+.
Increase in absorption of Ca⁺ causes constipation, lack of appetite, probably because of depressed contractility of muscle wall of gastro intestinal tract. This effect the short term regulatory and long term regulatory system for feeding
In order to maintain the pH and protect the wall from bacterial action, the secretion of mucous increases. At the same time movement of large intestine increases to push forward the faecal matter.
All these factor leads to disturbed rhythm of large intestine. The period of constipation is followed by diarrhea.
As a remedy for these disturbances Enema is used in naturopathy.

Hip bath : Specially designed tub is filled with temperate water or hot water. Person sits in a tub keeping his legs and hands out of tub. Mud pack and cold pack over umbilical region are alternative of hipbath. Duration : 5 min to 15 min depending on environment and body constitution. Temperate water (50-68°F / 10-20°C). Hot water (25 -30°C)

Hot foot bath / cold foot bath : A big bucket is used for this purpose. For hot footbath both feet should be dipped in hot water. While hot bath body is covered with blanket. For cold footbath both feet should be dipped in cold water. For alternative hot water and cold water foot bath both feet should be dipped in hot water alternatively with cold water. Start the process always with hot water. Duration : 20-45 min (Hot bath) depending upon environment. Cold bath: 5 min to 10 min depending upon environment Hot and cold alternating : 3 min Hot bath alternately with 1 min cold bath whole process should be done for 20 min.

Whole body Hot bath / Cold bath : Person rest in a bathtub filled with hot water or cold water keeping his head out of water. Temperature of hot water should be up to toleration limit. Duration : Hot bath: till sweating occur . Cold bath : 3 min to 8 min depending upon environment

Spinal Pressure Bath : A stream of hot and cold water is released over spine of person. Start the process always with hot water. Duration : Hot water 3 min and cold water 1 min for 20 min.

Mud therapy: Cleaned soil is immersed in water and is kept overnight. It then becomes mud. This mud is utilized as local mudpack over head, neck, abdomen, and upper limb or lower limb. In some cases this puffy mud is applied over whole body. Duration : 15 min to 30 min approximately, depending on environment.

Sun bath : Person should be in relaxed manner in direct sunlight. For sun bathe, person has to rest under medical supervision in direct sun light. To avoid sunrays directly over eyes, it should be kept covered by clothes or goggles. Duration : 15 to 45 min depending upon environment.

Cold sheet wrapping: A dry blanket is spread over cot. Then a thin bedsheet, dipped in cold water is spread over it. The person is made to lie on this cot. The entire body except head is well covered by wet sheets. Then blanket is wrapped over the body and pinning them well with safety pins. Duration : Till sweating occur 20 to 30 min depending upon environment.

Chlorophyll Bath : Banana leaves are used for this purpose. Process for this bath is - spread the dry blanket over the cot then spread dry cotton bedsheet over it. Then spread banana leaves over it. Person is made to lie over banana leaves. The entire body is covered with banana leaves. Over this bedsheet and blanket are wrapped using safety pins Duration : Till sweating occurs 20 min to 30 min depending upon environment.

Massage : Mustard oil, coconut oil, sesame oil, and olive oil are used for massage. Pressing, tapings, rubbing, bending, stretching, and vibrating with oil are steps of massage. Duration: 30 min. to 45 min. approximately.

Steam bath : Person sits over bench in a steam chamber keeping his head out of chamber. Steam of plain water is released in that chamber. While taking steam bath cover the head with wet clothes. Duration: 5 min to 10 min depending upon environment.

Sauna bath : Person sits in sauna chamber. Temperature is maintained about 800c to 900c. Before taking sauna bath cover the head with wet clothes. Duration : 5 min. to 10 min. depending upon environment.

Enema: Person lay on enema table in right lateral position. The enema table is inclined towards head side. Enema pot is kept 3 feet above enema table. It is filled with lukewarm or cold water. Well-lubricated nozzle is gently inserted in to the anal opening.

Belt: Hip and abdominal region are prominent site for fat deposition. The person stands on the platform and keeps vibrator belt over hip, waist, abdomen, and buttocks simultaneously. Through friction metabolic rate increases, which results in decrease in adipose tissue, helping in, reducing the fat, over hip and abdominal region.

Roller: Roller is non-thermal methods of hot therapy. It is equipped with revolving system of wood baton. It can be conferred from toe to neck region slowly on posterior side. This stimulates the neuromuscular system.