Does underarm body odor have a genetic factor ?

Recently there has been interest in the theory that underarm-produced body odor could have a genetic factor, and there has been some interesting research into this, using monozygotic (identical) twins to study the hypothesis.

In a 2005 study, the aim was to use a group of human 'sniffers' to match underarm odor samples from identical twins who did not co-habit (so as to avoid cohabiting factors being a factor). They did indeed find that identical twins underarm odor samples were matched by the human sniffers more often than chance would dictate. Non-identical twins were also more often matched, but not as often as identical twins.

Some quotes from the study :

The idea that body odor reveals information about both genetic identity and genetic similarity is most readily tested by examining odor in twin pairs...

... Here we show that odors of identical twins (but not dizygotic twins) can be matched by human sniffers at rates better than chance, even when the twins are living apart. In addition, matching frequencies for identical twin odors were not significantly different from those for duplicate odors from the same individual. These results indicate an important genetic influence on body odor and the potential for developing technologies for human odor printing in relation to underlying genotype....

...For example, it is thought that body odor carries cues of genetic similarity, which may be used in mate selection...

...Environmental influences on individual odors are well known and include effects of diet, disease , parasitic infection, and social or reproductive status...

...While dietary influences are likely to be most relevant in humans, any environmental influences arising from cohabitation could potentially confound any putative odor similarity determined by genetic effects...

...We collected axillary odors on cotton pads worn overnight in the twins' own homes and delivered to us by hand the following morning...

...Female body odors may be more variable than those of males as a result of menstrual cycle influences...

...Possible sources of this effect are genes within or linked to the major histocompatibility complex (MHC). Although this requires further research, MHC genes appear to influence odor preferences in many vertebrate species including humans...

http://www.ncbi.nlm.nih.gov/pubmed/18682364

A study in 2009 examined the same hypothesis using identical twins, this time comparing samples biochemically, testing each sample for carboxylic acids, which are known to be a source of axillary body odor in humans.

In humans, a correlation between odour preferences and the HLA type of both the odour donor and the odour evaluating individual has been shown (,Wedekind et al. 1995; ,Wedekind & Füri 1997). Therefore, in humans an association between body odour type and genes in the HLA locus appears to exist. Thus (i) it has been proposed that mice secrete a specific pattern of volatile fatty acids associated with their MHC type, (ii) human body odour appears to be influenced by genes in the HLA locus and (iii) a specific pattern of odorant fatty acids in human axilla secretions is strongly influenced by genetic factors (our current finding). The key challenge for the future is to establish whether the genetic factors contributing to these analytically observed profiles of fatty acids reside at least partly within the MHC/HLA locus in humans as they do in mice.

http://rsif.royalsocietypublishing.org/content/6/33/377.long

It should be remembered that neither studies will take into account malodorous biochemical systemic body odors like TMAU, since they will not be aware of such sources of odor. The first study told the testers not to eat certain foods known to cause body odor, but this was so diet wouldn't be a factor. Nevertheless it is likely that in many body odor cases there probably is a strong genetic factor, even if it is a susceptibility to a particular type of bacteria ecology under the arm. And of course most systemic body odors probably have a strong genetic factor.