There is some recent evidence that using nasal sprays to wash out virus from the nose and throat, or improving immune function through increasing exercise and managing stress, could reduce the frequency and severity of respiratory infections. To investigate this, researchers undertook a large-scale randomised trial to compare the effectiveness of two different types of nasal spray and an online resource providing advice on physical activity and stress management.
Paper: ‘A randomised multi-arm, open label trial of nasal sprays and a behavioural intervention for respiratory infections in primary care (The Immune Defence Study)’ by Professor Paul Little et al. in The Lancet Respiratory Medicine