Body odor seems to be a phenomenon of great importance to modern men, women and particularly to those youngsters who are just emerging into the world of physical adulthood. By body odor, we of course mean the unpleasant smell from underarms, groin or feet, although the last is usually thought of separately.
Cause
Body odor is produced by the action of skin bacteria on sweat. Human skin produces two kinds of sweat, the cooling watery liquid produced by the eccrine glands and the milky secretion of the apocrine glands. We have two or three million eccrine glands that cover our body, and eccrine sweating starts from birth. Newborns also have apocrine glands covering their entire bodies, which produce the 'baby smell' (not that one, the other one). Most of those disappear soon and the rest are turned off. These glands don't start working again until the onset of puberty, about 8 for girls and 9 for boys. When our bodies mature, the apocrine sweat glands number a mere 2000 or so and are concentrated in the groin and armpits; some are also on the scalp and a few other places. Apocrine secretion is stimulated by hormones, and by fear and stress as well. Stress sweating occurs mainly in the underarm areas, feet and palms.
It's the apocrine secretion that causes most of the odor problem. Certain bacteria (corynebacteria and micrococci) feed on this stuff and produce the pungent odor we have been taught to fear and abhor for its social consequences, most especially, but not only, in the U.S.
Control
Body odor can be controlled effectively by good personal hygiene. Wash at least once a day and after exercise. If you think for any strange reason that it is good not to wash your scalp, you may be right, but your head will soon stink. Bacteriocidal soaps may help. Change clothes often and wash them well to kill the bacteria that transfers into the cloth from your skin. To get you through a stressful day, however, you may want to use a commercial product. Those often combine the effects of deodorants to cover up BO with more pleasant fragrances, antiperspirants that act to control the sweating itself, and bacteriocides to suppress the bacteria. There is no complete or perfect solution, however; the bacteria grows back quickly, the sweating is not entirely stopped and the odor in not entirely overwhelmed for very long.
In history
The ancient Egyptians were apparently the first to come up with combinations of citrus oils and spices that could be applied to mask body odor without adding to the problem by turning rancid. They also discovered that shaving armpit hair reduced odor. (The hair provides a large surface area for bacterial growth.) Until the 19th century, perfume was the basic way to deal with body odor.
In the 1800s, effective commercial products for dealing with body odor began to appear, but the market really skyrocketed after the turn of the century when American advertising convinced people that social success was not to be had unless body odor was controlled. The euphemistic "B.O." was first used in ads for "Odo-ro-no", a product for women that was thrust into public awareness by an "always a bridesmaid, never a bride" campaign that made BO the horrible social villain that we know it as today. (Listerine soon jumped on this marketing bandwagon as well.) At the time, that was a rather shocking campaign, because body odor had always been only very indirectly hinted at in advertisement. Since Odo-ro-no, however, there's been no looking back by the deodorant industry as far as aggressive marketing is concerned.
Economic significance
The top six deodorant/antiperspirant products in the U.S. grossed nearly a billion dollars in sales in 2000. Worldwide sales of these products totaled 8.5 billion USD in 1999 and global demand for 2017 is about 14 billion. I wonder what else the world could do with 14 billion dollars. Because all deodorant products have the same active ingredients and work the same way, companies depend on 'product differentiation' to fight each other for market share.
Building upon growing public concern over chemical effects on health, the new wave in marketing is the 'natural' product that may include aloe, coriander or pick your favorite natural-sounding thing. Alum, a mineral crystal, is also being sold in various sizes and shapes as deodorant stone or deodorant crystal. It is supposed to work as an astringent to close up the sweat pores and reduce sweating. One does have to wonder whether wearing stones in your armpits is really worth the effect.
http://chnm.gmu.edu/features/sidelights/whoinventedbo.html
http://www.drgreene.com/21_907.html
http://www.pg.com/everyday_solutions/common_feature.jhtml?category=skin&rc=-5
http://www.ecrm-epps.com/Expose/V3_7/Global%20Closeup.asp
U.S. Sales data and projections