Olfactory training is developed for people who have partly or completely lost their sense of smell (olfactory dysfunction). Participants expose themselves to odours twice daily for usually 12 weeks or longer. It has been proven to effectively help people improve their sense of smell. However, when abnormal flavour perception is reported it may involve not only a dysfunctional sense of smell, but also taste and trigeminal perception (e.g. burning from chilly, cooling from mint, etc.). The stimulation of multiple sensations can theoretically enhance overall flavour perception. Therefore, we propose a pilot study to test the feasibility testing multi-sensation flavour impairment training approach using chewing gum that target sensations of smell, taste and trigeminal. This will be in comparison with an existing olfactory training approach.

Individuals (aged 18 to 65) with changed flavour perception (self-perceived, within 3 months to 2 years) will be invited to take part in this study. Participants will be randomly and evenly allocated to 3 groups which are: flavour impairment training using chewing gum (FIT), olfactory training (OT) using smelling strips, and a waiting list control group (CTR) (delaying FIT training for 12 weeks). In the first two groups, a 12-week training will be conducted. The training will be undertaken twice a day (in the morning and evening). All participants will use four flavours in a pre-determined and randomised order. One flavour of chewing gum (FIT group) or smelling strips (OT group) will be used each time. Each training session is expected to last around 3 minutes. In addition to the training, all participants will be asked to pay two visits to the lab, once before and once after completing the 12-week training, or the 12-week wait, to evaluate their flavour (smell, taste and trigeminal) perception capability. Participants will also be asked to conduct flavour perception tests at home before and after training following instructions to evaluate if their flavour perception capability has improved due to the training. The OT group and the CTR group will be offered the FIT treatment after they have undertaken the 12 weeks of their study group allocation.

Eligibility will be checked via an online questionnaire, where information of flavour perception impairment (self-report), chewing gum consumption habit, potential allergy to chewing gum/smelling bottle ingredients, and difficulty in chewing gums will be checked according to the inclusion and exclusion criteria .

Eligible participants will then be contacted via email for session time confirmation and taking consent. Upon their first visit to the lab, written consent will be taken, and training kit will be given to them.

Participants will be asked to pay two visits to the lab - to evaluate their smell perception using Sniffin' Sticks following a standard protocol (Rumeau et al., 2016) and taste perception using filter-paper disc (Nishijima et al., 2013). Upon their first lab visit, they will taste the four flavours (1 tablet per flavour) of the chewing gum that will be used in the following training. They will be given a questionnaire to indicate their perception and liking of all flavours. If there is any flavour, they find particularly disturbing that they do not wish to use to conduct the training, they have the opportunity to withdraw. Please see Fig.2. participant activities for lab visits and training at home. For both lab visits, participants will be given aromatic sticks to sniff to evaluate their Threshold, Discrimination and Identification (TDI score) of olfactory functions. Participants will also be given filter-paper discs of four tastes of sweet (sucrose), salty (sodium chloride), sour (citric acid) and bitter (quinine), and two trigeminal of cooling (menthol) and hot/burning (capsaicin) to evaluate their identification capability and threshold of taste and trigeminal sensations. Each session is expected to take up to 2 hours. On their first lab visit, participants will also be given logging-in information (by participant number) to an Xerte webpage so that they can access training protocol and their flavour selection if needed. Subsequently to the two lab visits, participants will be asked to conduct two at-home tests (once before and once after the 12-week training/waiting) to evaluate their smell, taste and trigeminal perception. For both OT and CTR groups, participants will be offered chewing gum training kit on their second lab visit.

Inclusion Criteria:

• • Aged between 18 and 65 years male and female

  • Have impairment in smell and/or taste (with a medical diagnosis or self-perception of between 3 months and 2 years)
  • Were able to smell and taste normally prior to the impairment (we anticipate that participants will have experienced the condition following a viral infection or idiopathically, etc)
  • Voluntary participation in the study
  • Willing to travel to Nottingham for 2 lab visits
  • Able to give informed written consent
  • Having not taken part in olfactory training or related research in the last 3 months or any study providing an inconvenience allowance.

Exclusion Criteria:

• • Physical damage in oral and/or nasal cavity due to surgery, trauma, etc.

  • Active infection with a virus that impedes smell and/or taste perception, sinonasal diseases, Parkinson's disease
  • Chewing or biting difficulty that would restrict chewing gum regularly
  • Allergy to chewing gum ingredients
  • Pregnancy or lactating
  • Having taken part in a research study in the last 3 months involving invasive procedures or an inconvenience allowance (this must remain for ALL UoN FMHS UREC approved studies)

All aspects

April 2025- indefinitely

Information will be available on request.