Olfactory training
All patients included during this study received OT as a therapy for their smell loss.11–13 Olfactory training is defined as conscious sniffing of (usually four) different odours twice a day for at least 15 seconds each.13 Participants either received: (i) four multi-molecule substances with a dominant scent of the odours stated hereafter for the entire study period (rose odour, phenyl ethyl alcohol; eucalyptus odour, eucalyptol; lemon odour, citronella; cloves odour, eugenol), (ii) four single molecule substances for the entire study period (anise odour, anethol; eucalyptus odour, eucalyptol; lemon odour, citronella; cloves odour, eugenol), or (iii) twelve multi-molecule substances, which were alternated twice every eight weeks as a group of four (first phase: phenyl ethyl alcohol, eucalyptol, citronella, eugenol; second phase: cinnamon, thyme, chocolate, peach; third phase: coffee, lavender, honey, strawberry). Previous studies have shown that the effect of OT in olfactory rehabilitation is consistent within studies that applied different training protocols.11–13