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What Is Hydroxyisohexyl 3-Cyclohexene Carboxaldehyde?
Hydroxyisohexyl 3-cyclohexene carboxaldehyde (HICC) is a synthetic fragrance compound belonging to the aldehyde family. It is a lipophilic molecule, meaning it has an affinity for oils and fats, which allows it to penetrate the skin barrier relatively easily. This ingredient is found in a small proportion of skincare products (approximately 0.2%), where it serves primarily to mask other ingredient odours or provide fragrance to the formulation.
As a fragrance component, HICC does not offer direct skincare benefits in the way that humectants or antioxidants do. Instead, its role is cosmetic—enhancing the sensory experience of using a product rather than treating a skin concern.
How It Works
HICC functions as a fragrance material by releasing volatile aromatic compounds that the nose perceives as a particular scent. Because of its lipophilic nature, it can penetrate the skin barrier and accumulate in skin tissue. This same property, whilst allowing for fragrance diffusion, also means the molecule is capable of triggering immune responses in susceptible individuals.
Clinical Evidence & References
Research indicates that HICC is a known contact allergen and is among the most potent sensitisers within fragrance mixtures. Patch testing studies have identified contact allergy to HICC in approximately 2.7% of patients tested in dermatology settings. The allergen is now included in baseline patch test series used by dermatologists internationally to screen for fragrance sensitivities.
Studies show that those with a history of atopy or facial eczema may be at higher risk of sensitisation. The relationship between patch test thresholds and real-world exposure thresholds has been studied, though individual evaporation rates and cumulative exposure can vary significantly depending on product formulation and use patterns.
Published Research
How to Use
If you have a known fragrance sensitivity or history of contact dermatitis, check product ingredient lists for HICC or avoid products listing fragrance components. Those with atopic skin or facial eczema may wish to consider unscented or fragrance-free alternatives. Patch testing on a small area before full application can help identify potential sensitivity.
Safety & Precautions
Frequently Asked Questions
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