Siddha system of medicine and treatment is popular in South India, especially widely followed by the peopleof Tamil Nadu formany centuries.

A popular myth attributed to the evolution of Siddha system of treatment is that the God Siva unfolded this knowledge of medicine to his consort, Parvati, who handed it down to Nandideva. He passed on the knowledge to Siddhars. Therefore, it is called 'Shiva Sampradayam' (tradition of Siva), or 'Siddha Sampradayam'. Instead of attributing the name to any one individual as the founder of this system, our forefathers wisely attributed its origin to the creator. Thus this knowledge of traditional medicine came to be known as Siddha System.

Siddha medicine, according to historical belief, dates back to around 2000 BC. The word Siddha means "an object to be attained", "Perfection" or "heavenly bliss".

Siddha system believes that the human body is composed of 96 Tatwas, 72,000 blood vessels and 1300 nerves. Besides these, there are 10 Nadi (main arteries), 10 Vayu (vital Pranas) and 10 Vegangals (natural functions). All of them play important roles in different functions of the body. The Siddha medicine also recognizes the role of three humors, called Mukkuttram (Vatham, Pitham and Kapham). These humors remain in a balanced state in normal healthy person and disturbance in their equilibrium leads to ill health. Siddha physicians base their diagnosis on Mukkuttram and Envagai Thervu (eight entities) i.e. Nadi (pulse), Na (tongue), Niram (colour), Mozhi (Voice), Vizhi (eyes), Sparsam (touch), Malam (faeces) and Muthiram (urine).

The treatment is mainly directed towards restoration of equilibrium of the three humors and for that purpose, one or more of the following cleansing procedures are adopted; (a) Vanthi (vomiting) (b) Bedhi (purgation) (c) Piccu (enema) and (d) Nasyam (nasal drops). For Vatharogangal (neuromuscular disorders) a specialized treatment called Thokkanam is practiced. Under this treatment, Siddha physician makes use of 12 types of medicated oils and five methods of applications. Siddha texts like 'Varma kannadi' and 'Varma suthiram' describe 108 vital points or vital neuro muscular junctions called as 'Varma nilaigal'. For the purpose of treatment, Siddha physicians apply pressure by specialized techniques at these areas to cure ailments.

According to the Siddhar's Science, the three humors in their normal order occupy respectively the lower, middle and upper parts of the body and maintain their integrity - the 'Vatham' in pelvis and rectum; the 'Pitham' in the area of the stomach and internal viscera and the 'Kapham' in the area of the respiratory organs, throat and head. It is also said that the characteristics of the three humors in the constitution of human beings are either hereditary or acquired. In scientific parlance, 'Vatham' comprehends all the phenomena, which come under the functions of the central and the sympathetic nervous system; 'Pitta', the functions of thermogenesis or heat-production, metabolism within its limits, the process of digestion, coloration of blood, excretion and secretion etc., and 'Kapha', the regulation of the heat and formation of various preservative glands.

The Siddhar's Materia Medica also is based on Humoral Pathology. It asserts that all substances of the animal, the vegetable and the mineral kingdom contain one or more of these three humors in their composition and therefore, diet should play an important role in the maintenance of these humors in men and women in preventing diseases or ailments. The patient should seek the advice of a physician in the matter of diet in the course of treatment.

The three humors maintain the upkeep of the human body through their combined functioning. When in disarray, they bring about diseases peculiar to their influence; when in equilibrium, freedom from disease; and when one or the other of the humors combine in such a way as to get deranged by aggravation diminution etc., disease or death may be the result. The humors by themselves are not inducing diseases in their normal functioning; but they cause disease if they are vitiated by other factors. Humors can be considered as components or parts of the human organism, and disease the outcome of external factors that cause disorder to the organism.

Materia Medica: The system has developed a rich and unique treasure of drug knowledge in which use of metals and minerals is liberally made.

According to Siddha approach to metals and minerals:
(1)There are 25 varieties of water-soluble inorganic compounds called 'UPPU'. These are different types of alkalis and salts.
(2)There are 64 varieties of mineral drugs that do not dissolve in water but emit vapour when put in fire. Thirty-two of these are natural and the remaining are artificial.
(3)There are seven drugs that do not dissolve in water but emit vapour when heated.
(4)The system has classified separately classes of metals and alloys, which melt when heated and solidifies on cooling. These include items like gold, silver, copper, tin, lead and iron. These are incinerated by special processes and used in medicine.
(5)There is a group of drugs that exhibit sublimation on heating and includes mercury and its different forms like red sulphide of mercury, chlorides of mercury and red oxide of mercury etc.
(6)Sulphur, which is insoluble in water, finds a crucial place in Siddha Materia Medica along with mercury for use in therapeutics and in maintenance of health.

Medical education of Five and a half years duration is imparted for undergraduates and three years duration for postgraduates like other system of Indian Medicines & Homeopathy.

Post-graduates training is imparted in six specialties of Siddha system viz. General Medicine, Pharmacology, Pediatrics, Toxicology, Pathology and Special medicine. At present, Siddha education is available at Govt. Siddha Medical College, Palayamkottai, Tamil Nadu; Govt. Siddha Medical College, Chennai, Tamil Nadu; Sri Sai Ram Siddha Medical College, Sriperumbudur, Kancheepuram District, Tamil Nadu; Velumayil Siddha Medical College at Sriperumbudur, Tamil Nadu and ATSVS Siddha MedicalCollege, Munchirai, Kanyakumari Dist., Tamil Nadu. Dr.T.Anandan, Research Officer, Siddha System of Medicine, Central Council for Research in Ayurveda and Siddha (CCRAS), Chennai