'Booting' and 'flushing' are terms used to describe an injecting behaviour in which the plunger is pulled back and the fluid (mostly blood and perhaps blood only) is re-injected. The behaviour differs from 'registering', which occurs before the drug is injected. Booting/flushing can produce subcutaneous and venous damage, and increases the risk for the spread of blood-borne viruses when used equipment is passed on to other injectors. The purpose of the study was to explore the extent of flushing, the context of flushing and IDUs' self-reported reasons for flushing. Data were collected through semi-structured interviews with 59 IDUs in Northern Ireland, who were recruited through various strategies. Respondents' ages ranged from 22 to 50 years and females comprised 34% of the sample. Mean length of injecting career was 8.3 years. A total of 46% reported flushing on a regular basis during some or most of the injecting career.

The results showed that flushing occurs for different reasons and, in comparison with research conducted elsewhere, is not associated solely with cocaine or speedball injection. Interventions designed to reduce the extent of flushing must take into account the various reasons for the behaviour.