Citronellol is a naturally occurring compound extracted from roses, geraniums, and citronella, and is often added to detergents, lotions, and perfumes to impart a subtle floral scent. (Image courtesy of Pixabay/CCL)
SEOUL, April 1 (Korea Bizwire) — A team of South Korean researchers has found that citronellol, a widely used plant-derived fragrance compound, may cause neurological toxicity when humans are exposed to it in high concentrations—raising fresh concerns about the safety of ingredients commonly found in cosmetics and household products.
Citronellol is a naturally occurring compound extracted from roses, geraniums, and citronella, and is often added to detergents, lotions, and perfumes to impart a subtle floral scent. While the U.S. Food and Drug Administration currently classifies it as safe and it has been touted for its calming aromatherapeutic properties, toxicological research on the substance has been limited.
But according to a new study led by Dr. Bae Myung-ae at the Korea Research Institute of Chemical Technology (KRICT), in collaboration with professors Hae-cheol Park and Soo-hyun Kim at Korea University, prolonged or excessive exposure to citronellol can trigger neuroinflammatory responses and behavioral impairments.
The findings, published in this month’s edition of the Journal of Hazardous Materials, mark the first time that the compound’s potential to cross the blood-brain barrier and induce brain cell damage has been clearly demonstrated.
Using both zebrafish (which share significant genetic similarities with humans) and rodents, the team observed that citronellol not only entered the brain but also increased the production of reactive oxygen species (ROS)—chemicals associated with cancer and aging—and activated inflammation-related signaling.
This led to damage of the blood-brain barrier, heightened immune responses, and signs of neuroinflammation, a condition linked to cognitive decline and neurodegenerative diseases.
Experiment on Citronellol’s Ability to Cross the Blood-Brain Barrier (Photo provided by the Korea Research Institute of Chemical Technology)
Advanced metabolomic analysis of the brain further revealed changes in tryptophan metabolism. The researchers found that citronellol shifted a key compound called kynurenine—normally capable of converting into neuroprotective molecules—toward the production of 3-hydroxykynurenine, a known neurotoxin.
These mechanisms were also confirmed in human brain organoids and lab-based blood-brain barrier models, reinforcing the relevance of the findings across biological systems.
In South Korea, citronellol is already classified by the Ministry of Food and Drug Safety as a potential allergen in cosmetics, and products exceeding a set concentration are required to label it accordingly—mirroring EU standards.
“This study shows that fragrances like citronellol may not only provoke allergic responses but also pose direct risks to the nervous system if overexposed,” said Dr. Bae. She emphasized the importance of further investigation into long-term and cumulative effects, particularly given the compound’s widespread use in consumer goods.
The research adds a new dimension to ongoing global discussions about the safety of natural ingredients, suggesting that even seemingly benign compounds warrant closer scrutiny when used at scale.
Kevin Lee (kevinlee@koreabizwire.com)
