Linalool (C₁₀H₁₈O) is a naturally occurring monoterpene alcohol found in essential oils such as lavender, coriander, basil, and thyme. In cosmetics, it is primarily used as a fragrance ingredient, prized for its floral, slightly citrusy scent. While linalool is widespread in personal care products, its biological activity and safety profile warrant closer scrutiny.

Antimicrobial Activity

Linalool has demonstrated antimicrobial properties, particularly against Gram-negative bacteria such as Pseudomonas fluorescens. Its mechanism of action appears to involve the disruption of bacterial membranes and interference with key metabolic processes. These findings suggest that linalool may contribute to the microbial stability of cosmetic formulations [1].

Safety and Sensitization Concerns

Despite being commonly used, linalool poses safety concerns related to oxidation. When exposed to air, linalool can oxidize and form hydroperoxides, which are recognized as potent skin sensitizers. These oxidation products, rather than linalool itself, are responsible for most allergic reactions associated with linalool exposure [2].

In clinical settings, linalool is one of the 26 fragrance allergens that must be labeled on cosmetic packaging in the European Union. Sensitization typically occurs with repeated exposure, especially in leave-on products or when formulations are poorly stabilized.

Conclusion

Linalool is a widely used fragrance compound with some antimicrobial potential, but its oxidation byproducts are well-established allergens. Formulas should ensure antioxidant protection or encapsulation strategies to reduce oxidation, and consumers with sensitive skin may benefit from avoiding products containing linalool.

References

1. Guo, F., Chen, Q., Liang, Q., Zhang, M., Chen, W., Chen, H., Yun, Y., Zhong, Q., & Chen, W. (2021). Antimicrobial activity and proposed action mechanism of linalool against Pseudomonas fluorescens. Frontiers in Microbiology, 12, 562094.
   https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7875898

2. Kuresepi, S., Vileno, B., Lepoittevin, J.-P., & Giménez-Arnau, E. (2020). Mechanistic insights on skin sensitization to linalool hydroperoxides: EPR evidence on radical intermediates formation in reconstructed human epidermis and 13C NMR reactivity studies with thiol residues. Chemical Research in Toxicology, 33(7), 1922–1932.
   https://pubmed.ncbi.nlm.nih.gov/32441093