Why can't body odor and halitosis sufferers and their 'loved ones' often not smell anything ?

One of the mysteries about body odor and halitosis, whether it is a surface problem or metabolic, is how so many can go around with body odor (or halitosis) apparently unaware of it, and also how often their 'loved ones' (whether genetic, or partners, or close friends) swear they can never smell the sufferer.

Sufferers have many theories about this, and at this point it is anyone's guess. Here are a few possibilities for now:

1: Some genetic or 'practical sensitivity gap' aspect. For instance, say the body odor is metabolic, perhaps some people with a similar enzyme flaw cannot smell sufferers. If not because of a genetic reason, then perhaps certain people have the same toxins circulating in their main system, and there's not enough of a 'sensitivity-gap' for them to detect sufferers. Or else their smell receptors for these smells (perhaps only via the skin/breath) are often near to saturation. This point is made because most sufferers seem to not have a problem in smelling normal smell fecal/gas smells. It is too complex to come up with one theory on this aspect, but it seems a very possible theory. This could not only apply to metabolic body odors, but to external body odor too. When you think about it, why do so many people who have 'washable' body odor not have someone (for instance a parent) to tell them 'you should wash' ? You have to think that not all their loved ones are heartless/too embarrassed to tell them. If a son/daughter/sibling/partner smelt sometimes of a body odor that they could wash off, would you not tell them ? There are still many hygienic people who go around with classic washable external body odor. The same seems to likely be true for both types of halitosis. If someone has permanent classic 'local' halitosis, why doesn't a 'loved one' tell them ? Perhaps because they can't smell them ?

2: Another theory mentioned is that people (sufferers and 'loved ones') get used to the smell. They perhaps become desentsitised to the odor(s), as one does with the fragrance in soaps or detergents, for example.

3: Perhaps most don't smell all the time. This seems likely for most, and also complicates diagnosis further, perhaps tying in with option 1. In Dr Pretis et al's 2007 paper Human breath odors and their use in diagnosis, he mentions that in the small TMAU group in the study, he could not smell any before the choline challenge, and only the 2 very 'low %' after the choline challenge. However, smelling of fecal or gas smells 1% of the time, when you don't know when you smell or the pattern, it's going to affect the sufferer's psyche 100% of the time. It seems possible that sufferers perhaps smell for certain minutes/hours at a time, or sometimes spontaneous for a few minutes. It's unclear at the moment. If the two factors were to do with how much enzyme someone had and how bad the 'smell' dysbiosis was, then someone at the top-end of each factor could smell more often than others. In that case someone only with the 'smell' dysbiosis could smell more often despite being 'normal'. But who knows.

There are probably many other theories which will be added as time goes by.

It is one of the most frustrating aspects of the problem, but in a strange way, since some people can't seem to smell sufferers, may be a cruel blessing for some, until the area of body odor and halitosis is properly researched. Especially the unknown metabolic body odor area. Perhaps it's a case that those suffering the same type of body odor or halitosis cannot smell each other. When Tammy Gobin (TMAU) went on the Tyra Banks Show, she later said in a Yahoo TMAU forum post that she could smell the lady on the show who claimed to have halitosis. Perhaps the other lady had a different type of odor problem, and so there was a clear 'detection sensitivity-gap'. However, so far at meetups everyone seems likely to be 'smell free/normal' for those few hours. And also perhaps smell-free within a certain unknown % of the population (perhaps as much as 15% ? more ?) at all times.

If it was to do with some sort of metabolic body odor or halitosis problem, it seems very possible that even 'carriers' of the flawed gene will not be able to smell sufferers. And neither will fellow sufferers. this seems to be confirmed by the feedback from body door and halitosis 'meet ups' - nobody smells anything even around people diagnosed with TMAU, with the exception of only a few passing occasions. So at least amongst this group (sufferers and carriers), someone with a metabolic body odor problem is likely to be 'smell free' to another sufferer, even if they are smelling at the time. On the upside, this means dating and friendship amongst this group would most likely mean 'no smells'.

There was a scientific paper in 1975, that found among a group that 7% could not detect trimethylamine. You can read the full document in PDF on that page
http://www.springerlink.com/content/l1hnv449m7267321/