Steam inhalation has not shown any consistent benefits in the treatment of the common cold, hence is not recommended in the routine treatment of common cold symptoms until more double-blind, randomised trials with a standardised treatment modality are conducted.
Effect of inhalation of hot humidified air on experimental rhinovirus infection.
Nasal inhalation of steam has been proposed as treatment of viral colds on the assumption that increased intranasal temperature will inhibit replication of rhinovirus (RV). The effect of steam inhalation on RV shedding by infected volunteers was examined in this study.
                Randomized controlled trial. Volunteers experimentally infected with RV were treated with machine-generated humidified air, which was either hot (active) or at room temperature (placebo). Viral shedding was assessed over the 4 days following treatment.
                Local hotel.
                Twenty volunteers from the university community who were susceptible to the challenge virus.
                Two 30-minute intranasal treatments, the first at 24 hours after inoculation and the second at 48 hours. The temperature of active vapor was 42 degrees C to 44 degrees C and of placebo vapor was 22 degrees C.
                Viral titers in nasal washings on each of 5 days following inoculation.
                Mean viral titers prior to the first treatment were 10(1.7) tissue culture infectious doses per milliliter in the active group and 10(1.5) in the placebo group. Mean titers for the next 4 days were 10(1.7), and 10(1.7), 10(1.2), and 10(0.9)/mL in the active group and 10(1.8), 10(1.9), 10(1.6), and 10(0.7)/mL in the placebo group (no significant difference). The proportion of volunteers who shed virus on each day was also similar in the two groups.
                Two nasal inhalation treatments with steam had no effect on viral shedding in volunteers with experimental RV colds.