Abstract Objective To determine the long-term effect of capsaicin and short-term effect of menthol on oral thermal thresholds. Design The thresholds for cold detection (CDT), warm detection (WDT), cold pain (CPT) and warm pain (WPT) were determined in 11 regular chilli-eaters (capsaicin group) and 11 control subjects that were closely matched for age, gender and ethnicity. The effect of menthol was determined by asking all 22 participants to suck a lozenge containing 0.52% menthol for 5 min. Results An ANOVA revealed a significant difference between the capsaicin and control groups ( P = 0.014), with the greatest difference in the WDT (capsaicin group 4.7 ± 2.7 [S.D.] °C; control group 2.3 ± 2.2 °C). Immediately after sucking a menthol lozenge there was a significant rise in the CDT (2.2 ± 1.1 °C to 5.9 ± 6.2 °C; P < 0.01) and WDT (3.6 ± 2.7 °C to 7.6 ± 4.4 °C; P < 0.001). Conclusions The consumption of foods containing capsaicin and menthol significantly alters thermal sensory thresholds in the oral cavity. Dietary habits should therefore be taken into account when intra-oral thermal thresholds are determined.