The confounding effect of background odors on olfactory sensitivity testing

Human olfactory sensitivity is known to vary significantly across subjects. Furthermore, environmental factors such as background noise and odor are known to affect target odor threshold scores but have not yet been fully delineated. We aimed to determine whether congruent and non-congruent background odor impaired target odor threshold scores. We performed odor threshold testing in 103 normosmic adults, using phenylethylalcohol (PEA) or linalool as target odors, under three conditions: (a) congruent target and background odors (e.g., PEA in the test and PEA in the background), (b) non-congruent target and background odors (e.g. PEA in the test and Linalool in the background) and (c) no background odor. Background odor was applied to the investigator's glove and testing was performed in an otherwise odorless room. We found that congruent background odors significantly impaired target odor threshold scores. Non-congruent background odors also impaired target odor threshold, but significantly more so with PEA as target and Linalool as background odor. The best threshold scores were obtained with no background odor. Comparison with Existing Method(s). At present, many testing environments may be contaminated with ambient background odors. We have shown that this may negatively affect odor threshold scores, particularly where background and target odors are congruent. We suggest that investigators performing odor threshold testing do so in well ventilated, odor free environments.