Introduction: People living with asthma need the knowledge and ability to respond to the demands of managing their variable symptoms. Supported self-management (including the use of written asthma action plans) improves health outcomes and reduces attacks. However, limited health literacy makes self-management difficult, which is especially challenging in low-to-middle-income countries (LMICs), where limited health literacy is prevalent. Tailored interventions, potentially including the use of mobile applications (apps), are needed to enable people with limited health literacy to realise the benefits of supported asthma self-management. Aims and Objectives: I aimed to 1). Systematically search for and synthesise evidence of clinical effectiveness of asthma self-management interventions targeted at people with limited health literacy and to identify strategies associated with effective programmes. 2). Explore experiences of living with asthma among people with limited health literacy in Malaysia, to understand the role of health literacy in influencing self-management decisions, the barriers to using evidence-based action plans, and how self-management can be supported. 3). Identify how to design an intervention underpinned by a theory of change. 4). Develop and refine a prototype asthma self-management app tailored to the needs of people with limited health literacy, optimising user experiences. Methods: Using the Six essential Steps in Quality Intervention Development (6SQuID) model, the programme of work consisted of the following: 1). Following Cochrane methodology, I systematically searched ten databases using a Population, Intervention, Comparison, Outcome and Setting (PICOS) search strategy. Selection of papers, extraction of data and quality assessment (using the Cochrane Risk of Bias tool) were duplicated. The primary outcomes were clinical (asthma control) and implementation (adoption/adherence to intervention). Analysis was narrative, due to the heterogeneity of studies. 2). I adapted an arts-based qualitative methodology, Photovoice. The study was conducted in four stages: 1: Initial in-depth interviews, 2: Photo-training and photo-taking activity, 3: Photo-interviews, 4: A photo-exhibition. I purposively sampled adults with asthma and limited health literacy from four primary healthcare clinics in a district of central Malaysia. Interviews were audio-recorded, transcribed verbatim, translated and analysed using two approaches: i) Narrative exploration of the experience of living with asthma among people with limited health literacy in Malaysia; and ii) Framework analysis informed by Sørensen's health literacy framework. Findings were interpreted in discussion within a multidisciplinary group. 3). With reference to the 6SQuID model, I used the study findings to design an intervention. 4). I adapted the Design Sprint method to an online format that took place over five days. Stakeholders provided insights on self-management issues (Stage 1), which informed the development of the prototype (Stages 2 to 4). Participants with asthma and limited health literacy tested the prototype and provided qualitative feedback, including a 'thinking-aloud' process triangulated with screen recordings of app browsing activities (Stage 5). Interviews were audio-recorded, translated and analysed thematically to identify utility and usability issues. Results: 1). I screened 4,318 titles and abstracts, reviewed 52 full-text studies, and included five studies. The risk of bias was low in one and high in the other four studies. Clinical outcomes were reported in two studies, both at high risk of bias. None reported uptake or adherence as an outcome of the intervention. Behavioural change strategies typically focused on improving an individual's psychological and physical capacity to enact behaviour (e.g., targeting asthma-related knowledge or comprehension). Less than half of the interventions used specific self-management strategies (e.g., written asthma action plans) tailored to limited health literacy status. A range of innovative approaches was used to provide education. 2). Twenty-six participants provided interviews; eight also completed the Photovoice activities. i) The concept of autonomy was the primary lens that pulled the data together. Through the lens of autonomy, three themes were identified: asthma as a life story, reclaiming identity in the network of everyday relationships, and redefining interactions with the health system and environment. ii) Health literacy was identified as a process of negotiating medical narratives and social practice. Participants with limited health literacy used various sources (e.g., social media) to access information about asthma and self-management but typically lacked appraisal skills. Doctor-patient communication had a pivotal role in helping patients understand asthma, though written action plans were rarely provided. Self-management decisions were influenced by socio-cultural norms, experiential knowledge and available social support. Specific challenges and recommendations in the use of action plans were identified. 3). Building on the previous literature, the systematic review and the qualitative study, I used Steps 1 to 4 of the 6SQuID model to define my intervention development. 4). Stakeholder discussions identified multi-level challenges. Five participants tested the prototype and described how the app influenced or could support self-management (utility): offering information, providing access to an asthma action plan, supporting medication adherence, and behaviour change. Specific usability issues addressed navigation, comprehension and layout. Conclusion: People with asthma experience challenges in coping with the variable symptoms of acute asthma. In the context of people with limited health literacy, understanding asthma and making decisions about self-management were heavily influenced by societal norms; therefore, interventions require a whole-system approach. Mobile technology may be an appropriate medium for delivering tailored self-management support at an individual level. Future studies are needed to test the feasibility of the prototype intervention in clinical practice.