Ciclosporin is an immunosuppressant drug used in dermatology to treat patients with severe or recalcitrant psoriasis, or with severe atopic eczema. It has important adverse effects, particularly on the kidneys, so careful counselling and monitoring are required. Ciclosporin was discovered in 1970 during a search for antifungal agents, and was found to have potent immunosuppressive properties. In the 1980s, it was licensed to prevent organ rejection following transplantation. Its beneficial effects on patients with psoriasis were found fortuitously. It has since been used to treat many immunologically mediated conditions.