Hexyl Cinnamal
The jasmine-apple note in countless shampoos — a Fragrance Mix II allergen, but one of the weaker sensitisers
INCIHexyl Cinnamal
- Category
- Fragrance
- Risk level
- medium
- Why it's flagged
- EU-labelled fragrance allergen and a Fragrance Mix II component
- Scent
- Jasmine- and apple-like; a cheap, popular fresh-floral note, especially in shampoo
- Fragrance Mix II
- One of the 6 components of FM II, which screens for "newer" fragrance allergies FM I can miss
- Relative risk
- A comparatively weak sensitiser — but very high exposure via daily shampoo use
- EU labelling
- Must be named above 0.001% (leave-on) / 0.01% (rinse-off); on the expanded 2023 allergen list
Look for these names on ingredient lists
This ingredient may appear under any of these names:
Commonly found in
Possible reactions
- Allergic contact dermatitis
- Scalp or hairline dermatitis from fragranced shampoo
- Facial rash around the forehead/temples that tracks with hair washing
- Possible cross-reactions with other cinnamic aldehydes
Top picks without Hexyl Cinnamal
Highly rated products whose ingredient lists don't include Hexyl Cinnamal.
As an Amazon Associate, AllerNote earns from qualifying purchases.
Always scan the actual label before use — formulations change.
Scan a product for this concern
What is hexyl cinnamal?
Hexyl cinnamal (INCI: Hexyl Cinnamal; also hexyl cinnamic aldehyde or HCA) is a synthetic fragrance aldehyde with a jasmine- and apple-like scent. It's a relatively modern, inexpensive fresh-floral note, which is why it became a workhorse fragrance in shampoos, conditioners, soaps, and mass-market personal care, with supporting roles in fine fragrance.
It's one of the six components of Fragrance Mix II (FM II) — the second-generation patch-test screen designed to catch fragrance allergies that the older Fragrance Mix I misses.
A weak allergen with heavy exposure
Here's the honest framing: hexyl cinnamal is a comparatively weak sensitiser. As an α,β-unsaturated aldehyde it can bind skin proteins (via a Michael-addition mechanism) and trigger Type IV contact allergy — which is why it's on the FM II screen — but molecule-for-molecule it's far less potent than cinnamal, eugenol, or isoeugenol.
What makes it clinically relevant is exposure, not potency. It's in so many daily-use, rinse-over-the-face products — especially shampoo — that cumulative contact is high. The classic presentation is scalp, hairline, forehead, temple, ear, and neck dermatitis that comes and goes with hair washing, because shampoo rinse-water carries the fragrance across all those areas.
Shampoo allergens rarely stay on the scalp. If your rash sits along the hairline, on the eyelids, behind the ears, or on the neck — the path rinse-water takes — a shampoo/conditioner fragrance like hexyl cinnamal is a strong suspect, even if your facial skincare is spotless.
How to spot and avoid it
- Read labels for Hexyl Cinnamal (or hexyl cinnamic aldehyde / HCA).
- Start with shampoo and conditioner — the biggest exposure — and switch to fragrance-free.
- Go fragrance-free for leave-on products too if you're FM II-positive.
- Patch test new products on the inner arm before scalp/face use.
Safer alternatives
- Fragrance-free shampoo and conditioner (e.g. Vanicream, Free & Clear, and other fragrance-free lines — verify the list).
- Fragrance-free body wash and soap.
- Lightly scented products built on non-allergenic aroma materials, if you tolerate them.
The bottom line
Hexyl cinnamal is a mild, ubiquitous shampoo fragrance — a weak allergen that matters mainly because of how much of it people meet every day. If you get rashes along the hairline, ears, or neck, the fix usually starts in the shower with a fragrance-free shampoo.
Was this article helpful?
One tap tells us what to write more of. No account needed.
Is this ingredient in your products?
Scan any cosmetic product to check for Hexyl Cinnamal and 30+ other allergens instantly.
References & further reading
- Fragrance Mix II and its components — overview DermNet
- Fragrance Mix II contact allergy — review PubMed / Contact Dermatitis
- CosIng / Regulation (EU) 2023/1545 (labelled fragrance allergens) EUR-Lex