Sense of Smell

The ability to smell is a prehistoric sense for humans and animals. It permits vertebrates and other organisms with an olfactory system to identify food, mates, predators, and provides both sensual pleasure as well as warnings of danger, such as spoiled food or chemical hazards. It is an important way we communicate with each other and our environment.

Many studies have suggested that the olfactory stimulation of fragrances produces immediate changes in blood pressure, muscle tension, pupil dilation, skin temperature, pulse rate and brain activity

Consequently, these electrical signals modulate the brain functions including memory, thoughts, and emotions.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5198031/