Abstract: A method, means, and apparatus to prevent and treat infections and disorders using germicidal light to inactivate and/or kill the organisms or cells that cause infections and other disorders. The method of treatment comprises irradiating the area to be treated using electromagnetic radiation of a germicidal nature. The method utilizes a previously unrecognized ability of germicidal light to penetrate the skin, nails, and other membranes sufficiently to successfully treat and prevent disorders. The electromagnetic radiation damages the organisms and cells that cause disorders such as skin and nail infections and renders them substantially incapable of reproducing. Without the ability to replicate the organism cannot continue to infest the skin and nails. The damage inflicted can also be sufficient to kill the organism outright. An infection is thereby prevented (if organisms are present, but infection has not yet begun), and the infection is cured if the infection already exists.