What does the smell of a bedbug consist of? - briefly
The scent emitted by bedbugs is a defensive blend of volatile compounds, chiefly the aldehydes (E)-2‑hexenal and (E)-2‑octenal, often accompanied by trace fatty‑acid odors.
What does the smell of a bedbug consist of? - in detail
Bedbugs emit a distinctive odor that becomes noticeable when the insects are crushed or disturbed. The scent originates from a mixture of volatile organic compounds released from their exocrine glands and internal tissues. The primary components are:
- Aldehydes – (E)-2‑hexenal and (Z)-2‑nonenal create a sharp, slightly sweet smell reminiscent of green apples or cut grass.
- Ketones – 2‑octanone contributes a faint, nutty note.
- Fatty acids – Isovaleric acid adds a sour, cheesy nuance.
- Phenolic compounds – 4‑ethyl‑phenol and related phenols impart a musty, earthy character.
- Alcohols – 1‑octen-3-ol produces a mushroom‑like aroma.
These chemicals are stored in the dorsal abdominal glands and are expelled as a defensive secretion when the bug is threatened. When the cuticle is ruptured, the internal fluids mix with the glandular secretions, releasing the full bouquet of volatiles.
Human detection thresholds for these substances are low; (E)-2‑hexenal can be perceived at concentrations as low as 0.5 ppb, explaining why the odor is often described as “pungent” despite the tiny amount of material present. The combined effect of the aldehydes, ketones, acids, phenols, and alcohols results in the characteristic “musty, sweetish” smell associated with bedbug infestations.