BackgroundEighty per cent of care home residents in the UK are living with dementia. The prevalence of faecal incontinence (FI) in care homes is estimated to range from 30% to 50%. There is limited evidence of what is effective in the reduction and management of FI in care homes.ObjectiveTo provide a theory-driven explanation of the effectiveness of programmes that aim to improve FI in people with advanced dementia in care homes.DesignA realist synthesis. This was an iterative approach that involved scoping of the literature and consultation with five stakeholder groups, a systematic search and analysis of published and unpublished evidence, and a validation of programme theories with relevant stakeholders.Data sourcesThe databases searched included PubMed, Cumulative Index to Nursing and Allied Health Literature, The Cochrane Library, Scopus, SocAbs, Applied Social Sciences Index and Abstracts, BiblioMap, Sirius, OpenGrey, Social Care Online and the National Research Register.ResultsThe scoping identified six programme theories with related contextâmechanismâoutcome configurations for testing. These addressed (1) clinician-led support, assessment and review, (2) the contribution of teaching and support for care home staff on how to reduce and manage FI, (3) the causes and prevention of constipation, (4) how the cognitive and physical capacity of the resident affect outcomes, (5) how the potential for recovery, reduction and management of FI is understood by those involved and (6) how the care of people living with dementia and FI is integral to the work patterns of the care home and its staff. Data extraction was completed on 62 core papers with iterative searches of linked literature. Dementia was a known risk factor for FI, but its affect on the uptake of different interventions and the dementia-specific continence and toileting skills staff required was not addressed. Most care home residents with FI will be doubly incontinent and, therefore, there is limited value in focusing solely on FI or on single causes of FI such as constipation. Clinical assessment, knowledge of the causes of FI and strategies that recognise the individualsâ preferences are necessary contextual factors. Valuing the intimate and personal care work that care home staff provide to people living with dementia and addressing the dementia-related challenges when providing continence care within the daily work routines are key to helping to reduce and manage FI in this population.LimitationsThe synthesis was constrained by limited evidence specific to FI and people with dementia in care homes and by the lack of dementia-specific evidence on continence aids.ConclusionsThis realist synthesis provides a theory-driven understanding of the conditions under which improvement in care for care home residents living with dementia and FI is likely to be successful.Future workFuture multicomponent interventions need to take account of how the presence of dementia affects the behaviours and choices of those delivering and receiving continence care within a care home environment.Study registrationThis study is registered as PROSPERO CRD42014009902.FundingThe National Institute for Health Research Health Technology Assessment programme.