Background: The use of mobile applications in dermatology to support remote diagnosis is becoming more important each day, particularly in rural areas where dermatology services are commonly managed by healthcare personnel with no speciality training. Objective: The aim of this study is to assess the reliability of mobile applications to support remote dermatological diagnosis, when used together with a dermatological ontology in underprivileged areas. Methods: A mobile application that allows characterization of skin lesions was developed. The experiment was conducted in a remote area without access to a dermatologist. A total of 64 dermatological queries were recorded in the mobile application. Results: The results showed that the probability of obtaining a correct diagnosis was between 64.4% and 85.6% and a confidence interval of 95%. Conclusions: This study demonstrates the implementation of a Teledermatology strategy based on mobile applications and domain ontology-driven knowledge base to provide timely assistance to healthcare professionals. This approach was found to be pertinent in the Colombian rural context, particularly in forest regions where dermatology specialists are not available.