Reference point
Breathe into a cupped palm the moment you wake up.
Do this before you read on. An entry only works when you have just smelled the thing.
Sour, with a sulphur note and a faint savoury layer. Much clearer than breath in the middle of the day.
The cause is saliva. At night the salivary glands almost stop, and for eight hours nothing washes the bacteria out of the mouth.
This entry shows that a smell can appear simply because something else is missing.
How to smell it
Breathe into a tightly cupped palm as soon as you open your eyes and smell at once. Then drink a glass of water, wait ten minutes and do it again. The difference is so large you will notice it even without brushing your teeth.
Why this one is hard
Because nobody wants to do it. Here the barrier is psychological, not technical.
Don’t confuse with
This entry
Morning breath
Animalic family
The same group of sulphur compounds made by anaerobic bacteria. Shrimp paste also has trimethylamine, giving a marine note.
Scientific note
Anaerobic bacteria in the mouth break down protein into volatile sulphur compounds: hydrogen sulphide, methyl mercaptan, dimethyl sulphide. Saliva normally washes them away and supplies oxygen that inhibits anaerobic bacteria. At night the flow of saliva drops to very low levels, and the concentration of these compounds rises steadily throughout the night.
In Vietnamese life
Rinsing the mouth with salt water in the morning is a long-standing habit in Vietnam, older than toothpaste. Salt does not kill all the bacteria, but it changes the osmotic pressure in the mouth and washes out most of the volatile compounds.