The sense of touch is the first to develop in humans at about 8 weeks into the gestation period. Touch stimulates the brain to release endorphins. Blood pressure and heart rate can be reduced by a touch.
When you breathe in through your nose, olfactory receptors are stimulated by chemical molecules suspended in the air and messages are sent to the olfactory bulb at the base of the brain. Smell is the sense most strongly linked to memory.
Every person smells things differently. This is because of the over 900,000 genetic variations of olfactory receptors. Good smells make you happier. Odors can accelerate puberty, attract mates and alter menstrual cycles in humans.
Dogs recognize and identify humans first by scent. Grizzly bears can smell food from up to 18 miles away.