Canine "Sniffin' Sticks" enable behavioural olfactometry to complement neurological examination in dogs

Olfactory function assessment in dogs remains limited compared to human medicine. This study aimed to develop a canine version of "Sniffin' Sticks" (canSSt) as a clinical behavioural olfactometry tool and to establish normative olfactory thresholds across sex, age, and cranial morphology in dogs. Eighty healthy client-owned dogs underwent clinical and neurological examination. A custom set of 15 felt pens containing serial tenfold eugenol dilutions (smell of cloves) was used to determine thresholds. Dogs were sequentially exposed to increasing concentrations. Behavioural responses were assessed by direct observation and independent video review. The test revealed high intra- and interobserver agreement (ICC 0.77-0.91). The mean threshold was dilution step 14.09 (SD ± 0.79), i.e., 8.71 ×  10^-14 g/ml eugenol. Exploratory psychometric modelling produced a lower threshold (IC₅₀) of 14.87 (95%CI 14.96-14.8), i.e., 1.43 × 10^- 14 g/ml. Empirical data revealed no significant effects of sex, neuter status, or skull type. However, olfactory sensitivity increased from juveniles to adults and declined in seniors, paralleling human patterns. The canSSt proved to be a clinically feasible tool for assessing olfaction, with dilution step ≈ 14 representing a normosmic reference within the used 15-item setup. Additional dilutions can capture the full olfactory spectrum in dogs.