Introduction Traditional Indian system of Siddha medicine practised over thousands of years has recently gained worldwide attention. Siddha medicine is the native medicinal system of Tamil Nadu. The present study aimed to document the various practises and medications followed by Siddha practitioners in treating various skin diseases form Katpadi taluk in the Vellore district of Tamil Nadu, India. Methods A qualitative and quantitative ethnopharmacological survey was carried out among 22 Siddha practitioners about herbal remedies and sastric (traditional) formulations prescribed by them for various skin diseases. Successive free listing method was utilized for documenting the healers’ knowledge on medicinal plants and Siddha formulations. The data were analyzed using Informant Consensus factor (Fic), use value (UV) and Informant Agreement Ratio (IAR). Results The healers prescribed a wide range of herbal remedies along with mineral based formulations. The study documented around 102 plant species and 23 sastric formulations for the treatment of 19 skin diseases. Based on the quantitative metrics fungal infections had high Fic value (0.98) followed by Acne vulgaris (0.96). Conclusion The study emphasizes the usage of numerous plant and mineral based medications for major skin illness by many Siddha healers of the region. Further, in-depth scientific analysis on these herbal and herbo-mineral formulations is required in order to validate their usage. In addition, the validations not only highlight the significance of Siddha medicine in treating the diseases but also highlight its importance and uniqueness. © 2016 Elsevier GmbH