04/04/2021
Olfactory training, also known as smell training, is currently the only known intervention to help with loss of smell (anosmia). The protocol was devised by Thomas Hummel of Dresden University Faculty of Medicine, and involves smelling four fragrant substances intentionally, for 10-30 seconds each, twice a day.
The odorants were selected based on Henning’s odor categories - a flowery odor (Rose or phenyl ethyl alcohol), a fruity odor (Lemon, Lemongrass or citronellal), an aromatic one (Clove or eugenol), and a resinous one (Eucalyptus, or 1,8-cineole).
Anosmia is most commonly caused either by trauma such as head injury, or viral infection of the upper respiratory tract.
This prospective clinical controlled study of olfactory dysfunction in 119 people was divided into two groups based on the origin of their smell loss. There were 72 in the post-infectious group and 47 in the post-traumatic group. Each of these groups was then further divided into intervention and control groups.
The intervention groups were instructed to perform smell training with the four odorants (phenyl ethyl alcohol, 1,8-cineole, citronellal and eugenol) twice daily for five minutes. During those five minutes they would smell each odor for 10 seconds and then take a 10 second break before moving to the next one. They continued like this for 16 weeks total. ��Their olfactory function was assessed at baseline, and then at 8 and 16 weeks, using the Sniffin’ Sticks battery test.
At the end of the study period, 68% of the post-infectious intervention group reported improvement (compared to 33% in the control group), and 33% of the post-traumatic intervention group also increased their sense of smell acuity (compared to 13% in the respective control group). ��This case-controlled study is one of several that show the efficacy of smell training to improve sense of smell in patients with olfactory dysfunction.
Konstandinidis et al, 2013
https://doi.org/10.1002/lary.24390
