Body odor or body odour is the smell of sweat and whatever bacteria are growing on the body. It is specific to the individual (except for identical twins in the same environment) and can be used to identify people, though this is more often done by dogs than by humans. An individual's bodily odor is influenced by diet, gender, heredity, health, medication, occupation, and mood. Body odor is associated with the hair, skin, breasts, armpits and genitals.
Diet can affect body odor. Japanese encountering Europeans for the first time found their odor particularly strong, and blamed it on the butter Europeans ate. The term bata-kusai (roughly meaning "butter reekers") was soon used to describe Europeans and still connotes anyone obviously Western. 
Many humans find the odor of Corynebacterium tenuis and C. xerosis in the apocrine sweat of the underarms offensive, so they use antiperspirants or deodorants. Antiperspirants stop the sweat, while deodorants kill or inhibit the bacteria. Although some choose to use an antiperspirant or deodorant because they view the smell offensive, others encourage perspiration and refrain from using antiperspirants, because they view it as a natural bodily reaction.
In the period of 1910-1920, the American advertising industry concluded that anxious, discontented consumers were better customers than satisfied ones. They initiated the now-familiar strategy of advertisements intended to foster anxiety about social status, and concern about personal deficiencies that could be remedied by buying the advertised product. In 1919, Odo-Ro-No became the first company to use the term "B.O." in an advertisement.
Pheromones and sexuality
Pheromones (Greek pherein, to carry + (HOR)MONE)
are chemical substances, which when secreted by an individual into the environment, cause specific reactions in other individuals, usually of the same species. They are found throughout the living world and are the most ancient form of animal communication.
Over the past few decades, universities, scientists and the media alike, have done research, experiments and studies on the significance of pheromones. These natural scents have been thought to play an important role in sexual communication. Animals and humans release biological chemicals in tears, saliva and perspiration. These aromas convey signals relating to mood, status, drive and health to the subconscious awareness of other individuals.
This is true as well in the animal world, as pheromones are consciously detected over considerable distances and serve at times in place of spoken communication. They help animals mark territory, recognize mates, and signal sexual interest. For example, female dogs in heat leave their pheromones and can attract male dogs over a mile away.
Similarly, studies have shown that females living together for extended periods of time will often find that their menstrual cycles start to synchronize. This is generally attributed to pheromones, though it is not certain what the evolutionary advantage to such synchronization might be.
In human men, the primary male pheromone (hormone) men unknowingly secrete that attracts women is Androstenone. Only men secrete this pheromone when they sweat.
In French, the term cassolette or "perfume box" is used to describe the natural scent of a woman. Alex Comfort, M.B., Ph.D., described this phenomenon in his 1972 publication, "The Joy of Sex."