A pioneering study by INRAE and IFCE reveals that horses can detect and emotionally respond to human emotional states through olfactory cues in sweat. By exposing horses to sweat samples collected from humans experiencing joy or fear, researchers observed that fear-related odors triggered heightened fear behaviors, increased stress markers like heart rate and cortisol, and reduced social engagement with humans. This demonstrates a cross-species emotional contagion mediated by chemical signals, suggesting that horses chemically “catch” human emotions, a phenomenon previously documented mainly in dogs.

These findings have significant implications for animal welfare and management, emphasizing the need for caretakers and trainers to be mindful of their emotional states during interactions with horses. The study also advances ethology by highlighting olfaction as a crucial channel for interspecies emotional communication, likely shaped by domestication. Understanding the chemical and neurobiological mechanisms behind this olfactory emotional signaling could lead to improved training methods and welfare practices, fostering stronger human–horse bonds and reducing stress in equine care.