The high morbidity of common colds means that their economic importance is considerable, with colds causing more loss of productivity than any other infection. As no effective prophylaxis is available, this trial was to test the hypothesis that sauna bathing can reduce the incidence of common colds. Twenty-five volunteers were submitted to sauna bathing, with 25 controls abstaining from this or comparable procedures. In both groups the frequency, duration and severity of common colds were recorded for six months. There were significantly fewer episodes of common cold in the sauna group. This was found particularly during the last three months of the study period when the incidence was roughly halved compared to controls. The mean duration and average severity of common colds did not differ significantly between the groups. It is concluded that regular sauna bathing probably reduces the incidence of common colds, but further studies are needed to prove this.

In a search for an effective prophylaxis against common colds, 25 volunteers were treated regularly with a standardised hydrotherapy programme for half a year, while 25 matched untreated persons served as controls. The frequency, duration and strength of colds were recorded. Resultsshow that there is a significant reduction in frequency of colds in the treated group. Similarly, this group seemed also to be affected less severely. The duration of common colds was shorter in the treated group which, however, failed to reach the level of significance. The prophylactic effects took about three months to become apparent. The underlying mechanism, by which the effect is mediated, is speculative at present. It is suggested that regular hydrotherapy represents an effective prophylaxis against common colds.