This is basic science. Hot substances warm and cold substances cool. Herbal formulas are a combination of hot and cold remedies that are balanced to fit the energetic makeup of the individual and their condition. The categories of ‘hot’ and ‘cold’ are not absolutes but guides on the path of balance. Though they are commonly classified alone they should be considered along with the other guna qualities of dry, unctuous, light, heavy, penetrating and soft. In fact, Charaka lists the six secondary actions (Upakrama) as energetic virya. The quality of virya is always more therapeutically important than rasa and vipaka. For example, a hot remedy such as fresh ginger (zingiber officinale) can be used to heat the body to cause a sweat that has the effect of cooling the body temperature. Conversely a cooling remedy such as kutki (Picrorrhiza kurroa) can be dispensed at a low dose to stimulate the digestion via its other light and dry properties and hence increase metabolism and heat. Other external influences such as the time of year that the herb is used, the constitution and condition of the patient as well as their subjective experience will all affect the physiological heating or cooling effect of the plant.
Heat warms, dries, invigorates and stimulates the tissues. This is Just as the sun on a hot day causes the blood to come to the surface of the body, so energetically hot herbs cause our metabolism to expand upwards and outwards causing the pores of the skin to open. Hot substances are high in the fire (tejas) element. Heat increases the metabolism, encourages circulation, cause sweating, light-head to treat cold, contracted and hypo or sluggish conditions. Beneficial to kapha and vata, it dries damp, phlegm and warms cold. As ‘like increase like’ pungent herbs encourage agni and digestive to pungent herbs encourage agni and digestion to function at optimum level. Herbs that are heating usually contains volatile oils or mustard glycosides that stimulate gastric secretions as well as assimilation of nutrients. Usna substances have a particular affinity for the heart, head, liver and lungs and are commonly used when they are imbalanced but may damage them. Pungent, sour and salty herbs tend to be heating.
Cold natured herbs cool, moisten and sedate the tissues and metabolism. Rather like the cold of a winter’s day causes you to shiver, energetically cold herbs contract the muscle and narrow the channels of circulation. They are high in the water element. Cold substances are usually used to treat ‘hot’, inflamed and hyper conditions. Cold benefits pitta while aggravating kapha and vata; cold-natured herbs soothe painful and inflammatory heat conditions. Digestion is easily damaged by cold-natured herbs and should be used cautiously when there is diarrhea and sluggish digestion from cold. Cold herbs have a affinity for the stomach, the kidneys and the bladder and can weaken them if used excessively. Bitter, astringent and sweet herbs tend to be cooling.
The classifications of hot and cold can be further separated into a hierarchy of degrees that will increase or decrease agni in the body. This emulates the vedic classification of agni representing the heating qualities of solar fire and soma representing the cooling qualities of lunar water. This is conveyed into tridosa theory with agni representing tejas and pitta, soma representing ojas and kapha with vata balanced in the middle as the regulatory prana.
Source by Dr Ram Mani Bhandari