Humans are often embarrassed when a dog trots over and starts sniffing at their groin, or pokes its snout in their butt. The dog has no idea that placing its nose in these parts of the human body might be offensive to some people, rather the dog is simply seeking information. The dominant sense for dogs is their sense of smell. Thus for canines reading scents is much like reading a written status report about the target of its sniffing. This is a common way to gather information from other dogs, and in many ways dogs treat humans as if they were similar to canines.
A special kind of sweat gland called apocrine glands produces scents that convey social information. These chemicals are called pheromones. Dogs and most other mammals, have their apocrine sweat glands spread over their entire body with higher concentrations in their genital and anal areas. The pheromone-releasing apocrine cells are even in the hair follicles, so a dog's fur gets coated with these chemicals and concentrated for easier identification by other dogs. Bacteria begin to act on these secretions almost immediately, modifying and intensifying the smell. Pheromone scents not only identify the sex, age, health and mood of the individual but also carry a lot of sexual information as well, such as where the female is in her estrus (menstrual) cycle, or if she is pregnant or having a false pregnancy
Comment: Now if we could only do something about all those psychopaths running banks, corporations and governments...