Background: Heated, humidified air has long been used by common cold sufferers. The theoretical basis is that steam may help congested mucus drain better and heat may destroy cold virus as it does in vitro.
Objectives: To assess the effects of inhaling heated water vapour (steam), in the treatment of the common cold by comparing symptoms, viral shedding and nasal resistance.
Search strategy: In this updated review we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library issue 4, 2005); MEDLINE (2003 to December Week 2 2005); EMBASE (July 2003 to September 2005); and Current Contents (current five years).
Selection criteria: Randomized controlled trials (RCTs) using heated water vapor in patients with the common cold or volunteers with experimentally induced common cold.
Data collection and analysis: All the articles retrieved were initially subjected to a review for inclusion or exclusion criteria. Review articles, editorials and abstracts with inadequate outcome descriptions were excluded. Studies selected for inclusion were subjected to a methodological assessment.
Main results: Six trials were included. Three found benefits of steam for symptom relief with the common cold (odds ratio (OR) 95% confidence interval (CI) 0.31; 0.16 to 0.60; relative risk (RR) 0.56; 95% CI 0.4 to 0.79). Results on symptom indices were equivocal. No studies demonstrated an exacerbation of clinical symptom scores. One USA study demonstrated worsened nasal resistance, while an earlier Israeli one showed improvement. One study examined viral shedding and antibody titres in nasal washings: there was no change of either between treatment and placebo groups. Minor side effects (including discomfort or irritation of the nose) were reported in some studies.
Authors' conclusions: Steam inhalation are not recommended in the routine treatment of common cold symptoms until more double-blind RCT trials are conducted.