There is intriguing evidence that humans communicate with unconscious chemical signals. That's not surprising because Evolution preserves techniques that work, particularly those that pass genes to the next generation. Animals use pheromones for 'discussions' with members of their species about topics like food, domination, territory and sex.
Pheromones can act at very small concentrations, below what the sense of smell can detect.
Moths, for example, can detect pheromones from other moths for several miles downwind. Odors and pheromones have a lot in common. They are both airborne chemicals detected by specialized nerve cells in the nose, but pheromones are generally defined as chemical signals between animals of the same species. In most of the species that have a VNO, it is wired to the amygdala, a primitive brain structure implicated in rage, emotion, fear and memory. The wiring then goes to the hypothalamus, the brain's headquarters for primitive responses to fear, food and temptation, not to mention blood pressure, heart rate, body temperature and a host of other critical physiological functions.