Keringer et al. 2020, Menthol can be safely applied to improve thermal perception during physical exercise — a meta-analysis of randomised controlled trials

Meta-analysis of randomised controlled trials (Scientific Reports 10:13636), 17 studies and 177 athletes. Menthol made exercise feel cooler: thermal sensation fell by a weighted mean −1.65 (95% CI −2.96 to −0.33; P = 0.014), an effect enhanced in still air (−2.86 without airflow), and thermal comfort tended to improve. Crucially it did not change the underlying thermophysiology — no meaningful effect on core temperature (+0.02 °C), sweat production (−24 ml) or heart rate — so menthol does not compromise the body’s warmth-defence responses. A performance (time-to-exhaustion) benefit emerged only in subgroups: higher-BMI athletes (+2.57 min), warmer environments (>31 °C), airflow present, and external (topical) application over internal delivery. The safety framing in the title refers to menthol not blunting protective heat responses, not to it being risk-free to over-rely on.