Olfactory training in patients with Parkinson's disease

PLoS One. 2013 Apr 17;8(4):e61680. doi: 10.1371/journal.pone.0061680. Print 2013.


Objective: Decrease of olfactory function in Parkinson's disease (PD) is a well-investigated fact. Studies indicate that pharmacological treatment of PD fails to restore olfactory function in PD patients. The aim of this investigation was whether patients with PD would benefit from "training" with odors in terms of an improvement of their general olfactory function. It has been hypothesized that olfactory training should produce both an improved sensitivity towards the odors used in the training process and an overall increase of olfactory function.

Methods: We recruited 70 subjects with PD and olfactory loss into this single-center, prospective, controlled non-blinded study. Thirty-five patients were assigned to the olfactory training group and 35 subjects to the control group (no training). Olfactory training was performed over a period of 12 weeks while patients exposed themselves twice daily to four odors (phenyl ethyl alcohol: rose, eucalyptol: eucalyptus, citronellal: lemon, and eugenol: cloves). Olfactory testing was performed before and after training using the "Sniffin' Sticks" (thresholds for phenyl ethyl alcohol, tests for odor discrimination, and odor identification) in addition to threshold tests for the odors used in the training process.

Results: Compared to baseline, trained PD patients experienced a significant increase in their olfactory function, which was observed for the Sniffin' Sticks test score and for thresholds for the odors used in the training process. Olfactory function was unchanged in PD patients who did not perform olfactory training.

Conclusion: The present results indicate that olfactory training may increase olfactory sensitivity in PD patients.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acyclic Monoterpenes
  • Adult
  • Aged
  • Aldehydes / pharmacology
  • Cyclohexanols / pharmacology
  • Discrimination, Psychological
  • Eucalyptol
  • Eugenol / pharmacology
  • Female
  • Humans
  • Male
  • Middle Aged
  • Monoterpenes / pharmacology
  • Olfactory Perception / drug effects
  • Olfactory Perception / physiology*
  • Parkinson Disease / physiopathology*
  • Sensory Thresholds / drug effects


  • Acyclic Monoterpenes
  • Aldehydes
  • Cyclohexanols
  • Monoterpenes
  • Eugenol
  • citronellal
  • Eucalyptol

Grants and funding

The authors acknowledge support by the German Research Foundation and the Open Access Publication Funds of the TU Dresden. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.