Siddha is a form of medical treatment of diseases using substances of all possible origins in a way that balances the possible harmful effect of each substance. This form of medicine was professed and practiced by siddhars who wrote their recipes on palm-leaves for the use of future generations. Siddha medicine was developed by outstanding Dravidians (ancient Tamils), locally called Cittars.

Preparations are made mainly out of the parts of the plants and trees such as leaves, bark, stem, root etc, but include also mineral and some animal substances. This form of medicine is still today well known in South India.

The use of metals like gold, silver and iron powders (Sanskrit bhasma) in some preparations is a special feature of siddha medicine, which claims it can detoxify metals to enable them to be used for stubborn diseases.