just like any other part on the body, the
male penis can and does sweat quite a bit
(especially near the testicles, which have
their own sweat glands that are very
active), which can cause a bad smell.
Also, in uncircumsized males (men that do
not have the foreskin of their penis cut
off), a waxy, white buildup called
"smegma" can occur. A little bit of
smegma can be okay (although most men find
it better to remove it as soon as they see
it), but a buildup can cause infections
which can then begin to smell bad.
The best cure for an odor-offending penis
is simply to wash it gently in warm water
and soap, being careful not to be too
vigorous or you might damage it.