Ksharasutra is a Sanskrit phrase, kshara stands for anything that is corrosive or caustic and sutra means thread. The ksharasutra is a medicated thread of alkaline in nature prepared by smearing it with various herbal and/or herbo-mineral substances.

Treatment with ksharasutra is a unique therapy mentioned in Sushrut Samhita of Maharshi Sushrut, the father of surgery, for the management of pedunculated mass and sinus or fistula. Description of Ksharasutra is also available in various Ayurvedic treatises like Charaka Samhita, Ashtanga Hridaya, Chakradatta, Bhavaprakash Samhita, Bhaishajya Ratnavali, Rasatarangini, Rasakamadhenu etc. Late Prof. P. J. Deshpande and his associates of Benaras Hindu University conducted an extensive study on ksharasutra preparation and its application with modern scientific parameters and outlined the present protocol of management of various types of fistulae and haemorrhoids with ksharasutra.

The commonly used ksharasutras are prepared with latex of Euphorbia neriifolia (snuhi), alkaline ash of Achyranthes aspera (apamarga) and powder of Curcuma longa (haridra). Various other ingredients are also used following textual references and researches for the preparation of ksharasutra and is prescribed accordingly depending on the clinical condition. Ksharasutras are dried up and exposed to ultra-violet (UV) rays keeping them in a specially designed cabinet. These ksharasutras are preserved in an air-tight container for six months.