When grass is cut, it is understandably a huge
trauma to the grass. It responds to this trauma by
releasing volatile organic compounds, which cause
the fresh cut grass smell. Volatile organic
compounds are carbon-based molecules that cause
very strong smells. The odor is really a distress
signal by the grass causing it to heal its wounds
faster or prevent bacterial and fungal growth.
A particularly interesting purpose of the
chemicals is that they attract big bugs to prey
upon the caterpillars that attack the grass. The
allergy likely has nothing to do with this smell.
Grass allergies are generally towards grass
pollen. When the grass is mowed, it kicks up all
of the pollen into the air which causes the
The pollen going to the air is a side effect of
grass being cut, but has nothing to do with the
smell of the grass itself. In fact, as grasses get
taller, they release more pollen, so not mowing
the grass could make allergies worse.
It is unlikely that chlorophyll has a
significant odor, especially when compared to the
volatile organic compounds released by the plant.
The class of organic molecules that chlorophyll
belongs to are not generally recognized as having
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