Does odour cross contamination alter olfactory thresholds in certain odours?

Objectives: To determine if: 1) there is cross contamination between odours tested on thresholds achieved, 2) a delay period is necessary between testing different odours. Methods: Thirty-five subjects underwent threshold testing with phenethyl alcohol (PEA), ethylmercaptan (MER), acetic acid (ACE), and eucalyptol (EUC) using serial logarithmic dilutions. On separate occasions subjects were exposed to high concentrations of PEA, ACE and EUC in random order for two minutes, and thresholds for all four odours re-tested. Pre- and post-high concentration odour thresholds were compared. Results: Exposure to high concentrations of PEA, ACE and EUC does not alter olfactory thresholds by more than 10^-2 for the other odours except in specific circumstances with ACE and EUC. Conclusions: There is limited cross contamination with ACE and EUC, which is avoided by specifying presentation order as: PEA, MER, ACE, EUC. Odours PEA, MER, ACE and EUC are recommended for olfactory testing.