it can make or break a relationship
They appear to work, but not in the way most people think. Male pheromones tend to make women relax and other men uptight and the same effect occurs for women with female hormones. They tell us who the competition is and who is a prospective mate and provide the emotion context to explore the possibilities.
Other smells like fear and disgust are actually contagious, again, providing important clues as to the context of the situation. Women tend to have a better sense of smell and there is some evidence they can actually smell when a prospective mate has a radically different immune system and can ovulate early as a result. By combining their genes their children will inherit increased immunity.