Cinnamal is the compound that gives cinnamon its distinctive warm, spicy smell. It’s a fragrance and flavoring chemical found naturally in cinnamon bark, and it appears on ingredient labels of everything from perfumes to toothpaste. You may have noticed the name while reading a cosmetic or food label, since regulations in many countries require it to be listed separately when present above certain concentrations. Its full chemical name is cinnamaldehyde, and the two terms are interchangeable.
Chemical Identity
Cinnamal has the molecular formula C₉H₈O. It belongs to a class of organic compounds called aldehydes, which are common in nature and often responsible for the aromas of plants and spices. You’ll also see it listed under several synonyms: cinnamic aldehyde, cassia aldehyde, 3-phenylacrolein, and 3-phenyl-2-propenal all refer to the same molecule.
The compound exists in two geometric forms, called trans and cis. The trans form is the one found naturally in cinnamon and used commercially. The cis form can appear when cinnamal is exposed to UV light, which becomes relevant for skin sensitivity (more on that below).
Where It Comes From
Cinnamon bark is the richest natural source. In cassia cinnamon, the type most common in grocery stores, cinnamal typically makes up 65 to 83 percent of the bark’s volatile oil. The exact concentration depends on the part of the plant: bark tends to have more than twigs, which contain roughly 65 percent. Ceylon cinnamon, the milder variety sometimes labeled “true cinnamon,” contains cinnamal as well but generally at lower concentrations.
For industrial use, most cinnamal is produced synthetically. The standard method reacts a benzaldehyde derivative with acetaldehyde under alkaline conditions. This process is efficient but generates byproducts that raise environmental and safety concerns, which has prompted research into biological production methods using engineered microorganisms.
Common Products That Contain It
Cinnamal shows up across a wide range of consumer goods. In cosmetics and personal care, it’s used in perfumes, decorative cosmetics, shampoos, toilet soaps, and other toiletries. Beyond personal care, it appears in household cleaners and detergents where a warm or spicy scent is desired.
On the food side, cinnamal is approved for use as a flavoring agent. The Council of Europe has included it on its list of substances permitted in foodstuffs. You’ll encounter it in baked goods, candies, chewing gum, and beverages. If you’ve tasted cinnamon-flavored anything, cinnamal was doing most of the heavy lifting.
Why It Appears on Labels
Cinnamal is one of a handful of fragrance ingredients that must be individually named on product packaging in the European Union rather than hidden under the generic term “fragrance” or “parfum.” The EU requires disclosure when cinnamal exceeds 0.001% (10 parts per million) in leave-on products like lotions and perfumes, or 0.01% (100 parts per million) in rinse-off products like shampoos and body washes. This rule exists because cinnamal is a recognized skin sensitizer, meaning it can trigger allergic reactions in some people.
Skin Sensitization and Allergies
Cinnamal ranks among the most common fragrance allergens. In a large European study that patch-tested over 3,100 randomly selected adults across five countries, 0.8% reacted positively to cinnamal, making it the third most common fragrance sensitizer after two other compounds. Among people already suspected of having contact dermatitis (a group more likely to be sensitive), positive reaction rates ranged from 1.2% to 1.9%, averaging about 1.5%.
The allergic reaction works through a specific mechanism. Cinnamal is small enough to penetrate the outer layers of skin, where it binds to proteins by attaching to certain amino acid building blocks, particularly lysine and cysteine. This binding creates a new molecular complex that the immune system recognizes as foreign. On first exposure, the immune system quietly takes note. On subsequent exposures, it mounts a visible response: redness, itching, and the bumpy rash characteristic of allergic contact dermatitis.
Sunlight can make this worse. UV radiation causes cinnamal to shift from its natural trans form to the cis form, which binds more aggressively to skin proteins. This means a product that doesn’t bother you indoors could potentially trigger a reaction after sun exposure, a phenomenon known as photocontact dermatitis. Even low concentrations of fragrance ingredients can act as photosensitizers under UV radiation.
How to Know If You’re Sensitive
The standard test is a patch test performed by a dermatologist. A small amount of cinnamal is applied to your skin under an adhesive patch and left for 48 hours. The site is then checked for redness or swelling at 48 and 96 hours. If you consistently develop rashes from scented products, cinnamon-flavored toothpaste, or cosmetics, cinnamal sensitivity is worth investigating.
If you do test positive, avoidance is the primary strategy. Read ingredient lists for cinnamal, cinnamaldehyde, cinnamic aldehyde, and cassia oil. Products labeled “fragrance-free” are generally safer than those labeled “unscented,” since unscented products sometimes contain masking fragrances that could include cinnamal.
Cinnamal vs. Related Cinnamon Compounds
Cinnamon contains several compounds that share similar names but are chemically distinct. Cinnamyl alcohol is the most commonly confused with cinnamal. While both come from cinnamon and both are recognized fragrance allergens, they are different molecules that trigger independent allergic responses. Being sensitive to one doesn’t necessarily mean you’ll react to the other, though overlap does occur. Hexyl cinnamal and amyl cinnamal are synthetic fragrance compounds used in cosmetics. Despite their names, they aren’t derived from cinnamon and have their own, generally lower, sensitization rates.
Coumarin is another compound found in cinnamon, particularly cassia cinnamon, that sometimes gets grouped with cinnamal. Coumarin contributes to cinnamon’s sweet, vanilla-like undertones rather than its spicy bite, and it raises different health considerations related to liver effects at high doses rather than skin sensitization.