Measuring breath: a patient sniffing their own hand is measuring nothing

Halitosis is one of the few conditions in which patients cannot judge for themselves whether the problem exists, and this generates two opposite errors.

Olfactory adaptation makes it impossible to perceive one's own odour: the olfactory system stops signalling a constant stimulus within minutes.

Home methods do not work. Sniffing one's hand after breathing onto it measures air exhaled from the lungs, not the air stagnating in the oral cavity, where halitosis originates.

The first error is therefore the patient who has halitosis and does not know, discovering it through an embarrassing comment. The second is the one convinced they have it without having it.

This second condition has a name: pseudohalitosis. The patient reports the problem, measurement does not confirm it, and the distress is real even though the odour is not.

Recognising it matters because the management differs. Prescribing mouthwashes and tongue scrapers to someone without halitosis reinforces the preoccupation rather than resolving it.

When the conviction persists despite repeated negative measurements and explanation, one enters halitophobia, which calls for a different approach and sometimes psychological involvement.

The organoleptic method remains the reference, because the human nose detects compounds instruments do not. It must, however, be standardised to carry any value.

The patient should avoid garlic and onion in the preceding twenty-four hours, use no perfume, neither eat nor brush in the two hours before, and have taken no antibiotics for some weeks.

Assessment is performed by having the patient exhale at a fixed distance and graded on a scale, comparing oral with nasal air: if the odour is present only from the nose, the origin is not oral.

Halimeters measure total volatile sulphur compounds and give a number, with the advantage of being objective and showable to the patient.

They do not, however, distinguish individual compounds, and the gas chromatography that does is confined to specialist centres. For ordinary clinical use, a halimeter alongside the organoleptic method is sufficient.

In summary: self-perception fails through olfactory adaptation, home methods measure the wrong thing, pseudohalitosis must be recognised because it needs a different approach, and organoleptic assessment must be standardised to mean anything.