Background: A perianal abscess is a collection of pus under the skin, around the anus. It usually occurs due to an infection of an anal gland. In the UK, the annual incidence is 40 per 100,000 of the adult population, and the standard treatment is admission to hospital for incision and drainage under general anaesthetic. Following drainage of the pus, an internal dressing (pack) is placed into the cavity to stop bleeding. Common practice is for community nursing teams to change the pack regularly until the cavity heals. Some practitioners in the USA and Australia make a small stab incision under local anaesthetic and place a catheter into the cavity which drains into an external dressing. It is removed when it stops draining. Elsewhere in the USA, simple drainage is performed in an outpatient setting under local anaesthetic. Objectives: To assess the effects of internal dressings in healing wound cavities resulting from drainage of perianal abscesses. Search methods: In May 2016 we searched: The Cochrane Wounds Specialised Register; The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library); Ovid MEDLINE; Ovid MEDLINE (In-Process & Other Non-Indexed Citations); Ovid EMBASE and EBSCO CINAHL Plus. We also searched clinical trial registries to identify ongoing and unpublished studies, and searched reference lists of relevant reports to identify additional studies. We did not restrict studies with respect to language, date of publication, or study setting. Selection criteria: Published or unpublished randomised controlled trials (RCTs) comparing any type of internal dressing (packing) used in the post-operative management of perianal abscess cavities with alternative treatments or different types of internal dressing. Data collection and analysis: Two review authors independently performed study selection, risk of bias assessment, and data extraction. Main results: We included two studies, with a total of 64 randomised participants (50 and 14 participants) aged 18 years or over, with a perianal abscess. In both studies, participants were enrolled on the first post-operative day and randomised to continued packing by community district nursing teams or to no packing. Participants in the non-packing group managed their own wounds in the community and used absorbant dressings to cover the area. Fortnightly follow-up was undertaken until the cavity closed and the skin re-epithelialised, which constituted healing. For non-attenders, telephone follow-up was conducted. Both studies were at high risk of bias due to risk of attrition, performance and detection bias. It was not possible to pool the two studies for the outcome of time to healing. It is unclear whether continued post-operative packing of the cavity of perianal abscesses affects time to complete healing. One study reported a mean time to wound healing of 26.8 days (95% confidence interval (CI) 22.7 to 30.7) in the packing group and 19.5 days (95% CI 13.6 to 25.4) in the non-packing group (it was not clear if all participants healed). We re-analysed the data and found no clear difference in the time to healing (7.30 days longer in the packing group, 95% CI -2.24 to 16.84; 14 participants). This was assessed as very low quality evidence (downgraded three levels for very serious imprecision and serious risk of bias). The second study reported a median time to complete wound healing of 24.5 days (range 10 to 150 days) in the packing group and 21 days (range 8 to 90 days) in the non-packed group. There was insufficient information to be able to recreate the analysis and the original analysis was inappropriate (did not account for censoring). This second study also provided very low quality evidence (downgraded four levels for serious risk of bias, serious indirectness and very serious imprecision). There was very low quality evidence (downgraded for risk of bias, indirectness and imprecision) of no difference in wound pain scores at the initial dressing change. Both studies also reported patients' retrospective judgement of wound pain over the preceding two weeks (visual analogue scale, VAS) as lower for the non-packed group (2; both studies) compared with the packed group (0; both studies); (very low quality evidence) but we have been unable to reproduce these analyses as no variance data were published. There was no clear evidence of a difference in the number of post-operative fistulae detected between the packed and non-packed groups (risk ratio (RR) 2.31, 95% CIs 0.56 to 9.45, I2 = 0%) (very low quality evidence downgraded three levels for very serious imprecision and serious risk of bias). There was no clear evidence of a difference in the number of abscess recurrences between the packed and non-packed groups over the variable follow-up periods (RR 0.72, 95% CI 0.22 to 2.37, I2 = 0%) (very low quality evidence downgraded three levels for serious risk of bias and very serious imprecision). No study reported participant health-related quality of life/health status, incontinence rates, time to return to work or normal function, resource use in terms of number of dressing changes or visits to a nurse, or change in wound size. Authors' conclusions: It is unclear whether using internal dressings (packing) for the healing of perianal abscess cavities influences time to healing, wound pain, development of fistulae, abscess recurrence or other outcomes. Despite this absence of evidence, the practice of packing abscess cavities is commonplace. Given the lack of high quality evidence, decisions to pack may be based on local practices or patient preferences. Further clinical research is needed to assess the effects and patient experience of packing.