Dogs have an extraordinary sense of smell, which allows them to detect subtle changes in human body chemistry. When you experience emotions like fear, happiness, sadness, or stress, your body releases specific hormones and pheromones that dogs can pick up on. For example, fear can trigger an increase in adrenaline and sweat production, altering your scent. Dogs' olfactory receptors—about 300 million compared to our 5-6 million—can distinguish these changes, enabling them to sense your mood and respond accordingly with comfort or alertness. Their ability to read body language and facial expressions also enhances their understanding of human emotions.