Abstract Background In the UK, people of South Asian origin with asthma experience excess morbidity, with hospitalisation rates three times those of the majority White population and evidence suggests that South Asian children with asthma are more likely to suffer uncontrolled symptoms and hospital admissions with acute asthma compared to White British children. This paper draws on data from The Management and Interventions for Asthma (MIA) study to identify the operation of barriers to optimal care and good asthma control for South Asian children. Methods The MIA study followed a multi-phase, iterative, participatory design, underpinned by the socio-ecological model. Findings presented here are from face-to face, semi-structured interviews with South Asian (Indian, Pakistani and Bangladeshi origin) parents and carers of a child with asthma (n = 49). Interviews were conducted in English or relevant South Asian languages using specially trained community facilitators. Data were transcribed verbatim and analysed according to the principles of interpretive thematic analysis, facilitated by the use of NVivo. Results Seven dimensions of candidacy are identified: identification of candidacy; navigation; the permeability of asthma services; appearances at health services; adjudications; offers and resistance and operating conditions in the local production of candidacy. The analysis demonstrates several ways in which a potential lack of alignment between the priorities and competencies of British South Asian families and the organization of health services combine to create vulnerabilities and difficulties in effectively managing childhood asthma. Conclusions Healthcare systems have a responsibility to develop services that are sensitive and appropriate to the needs of their communities. In South Asian communities, further efforts are required to raise awareness of symptoms and effectively communicate how, when and where to seek help for children. There is a need for improved diagnosis and consistent, effectively communicated information, especially regarding medication. Parents made several suggestions for improving services: presentations about asthma at easily accessible community venues; an advice centre or telephone helpline to answer queries; opportunities for sharing experiences with other families; having information provided in South Asian languages; longer GP appointments; extended use of asthma nurses; and better education for healthcare professionals to ensure consistency of care and advice.