Domestic researchers have proven the harmfulness of the fragrance 'citronellol,' widely used in daily products. Previously known as a safe ingredient, citronellol has been shown to induce neurotoxicity and behavioral disorders when exposed to high concentrations.
A joint research team led by Baehmyeong-ae, chief researcher at the Korea Research Institute for Bioscience and Biotechnology's Rare Disease Treatment Technology Research Center, along with professors Park Hae-cheol and Kim Soo-hyun from Korea University, announced on the 30th that they were the first in the world to elucidate the neurobehavioral disorders and toxicity caused by exposure to high concentrations of citronellol.
Citronellol is a natural fragrance component extracted from plants such as roses, geraniums, and citronella. It is known to provide aroma and psychological stability, and is used in various daily products, including cosmetics and detergents, as a relatively safe ingredient. The U.S. Food and Drug Administration (FDA) classifies this ingredient as a generally recognized as safe (GRAS) substance.
However, the research team's experimental results confirmed the neurotoxicity of citronellol. The team demonstrated that the aromatic component, after being absorbed into the body, crosses the blood-brain barrier (BBB) and damages brain cells using zebrafish and mice as model organisms.
Zebrafish, commonly used for behavioral analysis, showed increased anxiety responses as the concentration of citronellol exposure increased. Abnormal behavior was observed as the normal response of moving toward light diminished.
It was also confirmed that citronellol reaches the brain by passing through the BBB and generates reactive oxygen species, causing inflammation. Both reactive oxygen species and inflammation are known factors that impair neural and behavioral functions. Neuroinflammation induced by immune cell activation and damage to the blood-brain barrier were also observed.
Zebrafish and mice exposed to high concentrations of citronellol also showed changes in kynurenine, one of the neuroactive metabolites. Kynurenine can convert into two substances: kynurenic acid, which protects the brain, and 3-hydroxykynurenine (3-HK), which damages nerve cells. It was confirmed that citronellol induces the change of kynurenine toward the neurotoxic molecule 3-HK.
The Ministry of Food and Drug Safety designates citronellol as an allergenic ingredient in the cosmetic allergy labeling regulations. Similar to the European Union (EU), products must be labeled if they contain citronellol above a certain concentration. Products intended to be washed off, like cleansers, must have a concentration of 0.01% or more, while non-wash-off products like lotions must be labeled if they contain 0.001% or more.
The researchers noted, "This is a representative successful case of next-generation biomimetic technology utilizing zebrafish and human-derived biomodels."
The research results were introduced in the international journal 'Journal of Hazardous Materials' on the 15th.
References
Journal of Hazardous Materials (2025), DOI: https://doi.org/10.1016/j.jhazmat.2024.136965