Asthma is a chronic lung disease of the airways that makes breathing difficult. Worldwide, asthma is a leading disease among children and adolescents and a leading cause of hospitalizations among adolescents. Asthma self-management is a systematic procedure that allows educating, training, and informing patients to control their disease and avoid it when it is possible and reduce it when it is necessary. Nowadays, there is a need for technological tools for supporting different tasks within the process of asthma self-management, such as education, control, and monitoring, that help patients and their families improve their quality of life and reduce the direct and indirect costs. This work proposes Astmapp, a platform that relies on semantic and mobile technologies and recommender systems to increase the patients' knowledge about asthma regarding topics such as triggers, symptoms, activity restrictions, medications, among others, and to promote the asthma control by means of the monitoring of symptoms and parameters such as physical activity, heart rate, blood pressure, temperature, among others. Likewise, Astmapp recommends educational resources based on the preferences of patients and generates medical recommendations based on the symptoms and health status of the patient aiming to prevent asthma and reduce its exacerbation. Astmapp was evaluated in terms of its ability to recommend asthma educational resources relevant for the patients as well as to provide health recommendations. The evaluation results suggest that Astmapp has the potential to effectively support the asthma self-management process.