Reference point
Open a bottle of green dầu gió medicated balm and smell from a hand’s span away.
Do this before you read on. An entry only works when you have just smelled the thing.
An icy cold in the nasal cavity, with the sweet note of mint and the faint woodiness of camphor.
The cold is not caused by temperature but by the cold receptors being activated directly. Menthol binds to the very receptor the body uses to detect cold, so the brain receives a cold signal while the temperature has not changed. The smell here fools the body.
This is the standard reference for the whole medicinal family. Many other smells in the family are commonly described by comparing them with this balm, consciously or not.
How to smell it
Open a bottle of green dầu gió, hold it at least a hand’s span from your nose and smell gently. Don’t bring it close — at high concentration the cold completely drowns the smell and you learn nothing. Three short sniffs are better than one long one.
Why this one is hard
Because the intensity is so strong that there is no time to analyse. The technique is to lower the concentration: smell from a distance, or put a drop on paper and wait a minute before smelling.
Don’t confuse with
This entry
Medicated balm
Medicinal family
The same active ingredients, a different base. The liquid balm rises at once and is sharply cold; the balm in a wax base is slower and denser.
Scientific note
Dầu gió is not peppermint oil but a ready-made blend. The composition varies by brand, but the formula familiar in Vietnam usually contains menthol for the cold, camphor for the dry sharpness, and methyl salicylate for the warm medicinal note underneath.
It is the presence of all three groups at once that makes this balm different from a bottle of peppermint oil. Menthol acts on the cold receptors, camphor and methyl salicylate act on the nerves in other ways, so you get both a cold and a warm sensation in the same sniff.
That is also why it is a good reference for the medicinal family: it does not represent any one plant but a blended impression, and almost everyone who grew up in Vietnam carries that impression in memory.
The balm is placed in the top stage because that is the real impression, even though menthol boils at 212 degrees. The reason: most of menthol’s effect does not go through smell but through the TRPM8 receptor on the trigeminal nerve — a channel that signals instantly, regardless of how much of the molecule evaporates. The mouthwash entry goes into this in more detail.
In Vietnamese life
Dầu gió has been in almost every Vietnamese household for generations. That makes it one of very few smells the whole country shares as a common reference — ideal conditions for a reference point.