Study	Reason for exclusion
Anene 1996	Randomised controlled trial; children were not diagnosed with croup
Bollobas 1965	Not a randomised controlled trial; children were not diagnosed with croup
Cichy 1983	Not a randomised controlled trial
Connolly 1969	Randomised controlled trial; children were not diagnosed with croup
Couser 1992	Randomised controlled trial; children were not diagnosed with croup
Eghbali 2016	Randomised controlled trial; the intervention was L‐epinephrine
Faghihinia 2007	Randomised controlled trial; no usable results were presented (not clear how many children were in each group)
Faraji‐Goodarzi 2018	Randomised controlled trial; no relevant outcomes
Flisberg 1973	Not a randomised controlled trial
Freezer 1990	Not a randomised controlled trial; study was a retrospective chart review
Gill 2017	Not a randomised controlled trial
Goddard 1967	Randomised controlled trial; children were not diagnosed with croup
Haque 1981	Not a randomised controlled trial; children in the control group received no treatment
Havaldar 1997	Not a randomised controlled trial; children were not diagnosed with croup
Kelley 1992	Not a randomised controlled trial; study was a retrospective chart review
Kunkel 1996	Not a randomised controlled trial; intervention was epinephrine
Ledwith 1995	Not a randomised controlled trial; intervention was epinephrine
Martensson 1960	Not a randomised controlled trial
McDonogh 1994	Not a randomised controlled trial; study was a retrospective chart review
Mohammadzadeh 2014	Randomised controlled trial; intervention was epinephrine
NCT01748162	Randomised controlled trial; did not report any relevant outcomes
Novik 1960	Not a randomised controlled trial
Osváth 1994	Not a randomised controlled trial
Prendergast 1994	Not a randomised controlled trial; intervention was epinephrine
Rizos 1998	Not a randomised controlled trial
Roked 2015	Not a randomised controlled trial; study was a retrospective chart review
Ross 1969	Not a randomised controlled trial; study was a retrospective chart review
Serra 1997	Not a randomised controlled trial
Sumboonnanonda 1997	Randomised controlled trial; children in the control group received no treatment
Sussman 1964	Randomised controlled trial; children were not diagnosed with croup
Tal 1983	Randomised controlled trial; children were not diagnosed with croup
Tellez 1991	Randomised controlled trial; children were not diagnosed with croup
Wilhelmi 1976	Not a randomised controlled trial