| Methods | Randomised double‐blind placebo controlled trial with crossover design. | |
| Participants | 6 adults (2 female, 4 male) in Baltimore, USA, with ragweed sensitive asthma, defined by skin‐prick positivity. Tested out of the ragweed season. Asymptomatic and not on treatment. | |
| Interventions | 500mg once daily vitamin C for 7 days compared to lactose placebo. | |
| Outcomes | PD20 FEV1, PD35 SGaw, tested on day 7, 3hrs after dose of placebo/vitamin C | |
| Notes | Data not presented in an abstractable format, no reply from author to date. | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Adequate sequence generation? | Unclear risk | Method of randomisation not described |
| Allocation concealment? | Unclear risk | Method of allocation not described |
| Blinding? All outcomes | Unclear risk | Study described as double blind but method of blinding (e.g. identical placebo pill) not described |
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