Body odor is a uniquely personalized thing.
Just what kind of body odor each individual person has is determined
by a combination of a certain area of their genetic makeup called
the major histocompatibility complex and, partially by what they
eat. The basic composition of a person’s body odor remains the same,
however, and it has been suggested that one of the reasons for it is
to help us choose a genetically appropriate mate. Change in body
odor has also been linked to the development of certain cancers and
viral diseases.
The body odor fingerprint isn't the only thing scientists have
discovered about body odor. They found that the older people get
the worse they stink. A substance called 2-Nonenal has been
identified as the reason some people have a faintly greasy odor
about them. The substance has only been found in people over the
age of 40 and the older people get, the more of the substance the
body produces. Sweat itself is pretty much odorless, but the
bacteria that reacts with sweat is what produces the odor.