Local hyperthermia benefits natural and experimental common colds.

OBJECTIVE To determine whether inhaling fully humidified air at 43 degrees C gave more benefit to cold sufferers than inhaling air at 30 degrees C. DESIGN Randomised double blind trial. Setting--General practice and the common cold research unit. SUBJECTS 87 Unselected patients with typical acute nasal and upper respiratory symptoms (general practice study), and 84 volunteers aged 18-50 without a history of chronic or allergic diseases. INTERVENTIONS Subjects breathed from apparatus delivering 40 litres of room air heated to 43 degrees C or 30 degrees C and fully humidified (relative humidity 100%) per minute. End point--Reduction in severity of disease. MEASUREMENTS and main results--Patients recorded their symptoms (general practice study) and observers recorded symptoms and signs, weight of nasal secretions, isolation of virus, and antibody responses in volunteers. Patients treated for 20 minutes at 43 degrees C had in the succeeding days roughly half the score for symptoms of those treated at 30 degrees C. Volunteers treated for 30 minutes on three occasions when they were starting a cold showed an 18% [corrected] reduction in symptoms. Treatment of volunteers for 20 minutes at the onset of the cold and for 10 minutes on succeeding days showed no difference between 43 degrees C and 30 degrees C. CONCLUSIONS Nasal hyperthermia can improve the course of a common cold and also give immediate relief of symptoms.