Siddha comes from the word 'Siddhi' which is means 'perfection' or 'eternal bliss'. Agastyar or Agasthya, is believed to be the founding father of Siddha Medicine. Siddha focused on "Ashtamahasiddhi," the eight supernatural power. Those who attained or achieved these powers are known as Siddhars. There were 18 important Siddhars in olden days and they developed this system of medicine. Hence, it is called Siddha medicine. Thus this system connects both spiritual and physical and treats the person as a whole i.e. it concentrates the physical, psychological, social and spiritual well being of an individual The roots of this system are intertwined with the culture of ancient Tamil civilization.
The origin of Siddha system is attributed to sage Agastiyar. It is also believed that before the Aryan occupation of the Sind region and the Gangetic plain, Tamirapani, a highly organized civilization, dwelled on the banks of River Kaveri. This civilization is considered to be the source of Siddha system.

Siddha conferred the supernatural powers to siddhars , by virtue of which they employed their knowledge for benefit of mankind .The analogy between Siddha and Ayurveda -
1- Siddha methodology of treatment is analogous to Ayurveda system .According to human pathology , all diseases are classified on basis of Vatta , Pitta , Kapha . Imbalance of vata could be the root cause of all disease Significance of these three elements –
Vata – Internal vata corresponds to external air. It occupies region of Pelvis and rectum . Siddhars believed vata to be self-originated and identical to divine energy
Pitta - Internal Pitta corresponds to external heat . It occupies regions related to the stomach and the viscera. Pittawas believed to represent all the characteristics of fire
Kapha - internal kapha corresponds to external water. It occupies regions related to breath, the throat, and the head. Kapha was believed to supply moisture to the body and to give stability, adding to the strength of the body by increasing the firmness of the limbs .
2-The basic tenets of human body constituents- Earth , Water , Fire , air , and Sky , are common to both Ayurveda and Siddha . Location of elements in human body are –
Earth, present in - bone, flesh, nerves, skin, and hair;
Water, present in- bile, blood, semen, glandular secretions, and sweat;
Fire ,present in - hunger, thirst, sleep, beauty, and indolence;
Air , present in - contraction, expansion, and motion;
Ether , present in - interstices of the stomach, heart, neck, and head.
3- As in Ayurveda, siddha system also considers the human body as a conglomeration of three humours, seven basic tissues and the waste products of the body such as faeces, urine and sweat. The food is considered to be basic building material of human body which gets processed into humours, body tissues and waste products.

Therapeutic measures of Siddha system-
A.Therapeutic measures to cure diseases - Siddha medicine has been used for the management of chronic diseases and degenerative conditions, such as rheumatoid arthritis, autoimmune conditions, collagen disorders, and conditions of the central nervous system. Its effectiveness in those situations has varied.
B. The Siddha system has developed a rich and unique treasure of drug knowledge in which use of metals and minerals is very much advocated. Some idea about the depth of knowledge the system possesses in the field of mineral, materia medica can be found from the detailed drug classification, briefly described below:
There are 25 varieties of water-soluble inorganic compounds called 'UPPU'. These are different types of alkalies and salts.
There are 64 varieties of mineral drugs that do not dissolve in water but emit, vapours when put in fire. Thirty-two of these are natural and remaining are artificial.
There are seven drugs that do not dissolve in water but emit vapour on heating.
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, tine, lead and iron. These are incinerated by special processes and used in medicine.
There is a group of drugs that exhibit sublimation on heating and includes mercury and its different forms like red sulphide of mercury, mercuric chloride and red oxide of mercury etc.
Sulpher, 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.
The above classification shows detailed knowledge and study of minerals that this system has evolved for treatment. In addition there are drugs obtained from animal sources. The system has published a hand-book on Siddha treatment for common diseases and ailments.

The disease is treated in holistic manner by incorporating the techniques of Pranayama and Varman , while medical drugs constituted of herbal and mineral treatment . The following are -
Pranayama - refers to "breath." In Siddha medicine, breathingis considered to be the most important of all functions, providing vitality and freedom from disease.
Varman - Varma is an area of practice in Siddha medicine that is concerned with varmam. The varmam are points of intersection of bone, muscle, tendons, nerves, and blood vessels.
Herbal and Mineral treatment - The siddhars did extensive research on plants and devised methods by which plants could be harnessed medicinally. SSM have been categorized into three groups: plant products (mulavargam), inorganic substances (thathuvargam), and animal products (jivavargam), which are characterized by means of taste (suvai), quality (gunam), potency (veeryam), post-digestive taste (pirivu), and specific action (prabhavam).

Medicinal plants from SSM , used to treat respiratory diseases -
Kuppaimeni- leaf powder cures respiratory diseases. Its other actions include cathartic, anthelmintic, expectorant, emetic, anodyne, hypnotic, antimicrobial and wound healing properties.
Adathodai - It cures Bronchial asthma , Eosinophilia and cough .The plant also consist of anti-inflammatory ,antiulcer ,hepatoprotective and antiussive properties .
Celery-Keeral – The seed and Leaves are used to treat asthma and bronchits as well as liver and spleem diseases . It showedinhibitaory activity on Nitric Oxide production in-vitro.
Mukaratee – It treat asthma , heart disease , Kidney stone and colitis .

There are other medicinal plants that are used to treat chronic and acute ailments by SSM .
Watch out significance of Siddha System of Medicine by – Central Council of Research in Siddha