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Parfum, Limonene, Linalool, Citral. The last four words on the ingredient list of many creams and scented oils. They are there because of a clause in European cosmetics law, and from July 2026 that list is much longer.

The smallest line on the label

A cosmetic ingredient list under EU law reads from the top down in decreasing order of content. Water, oils, emulsifiers come first. Near the end is a collective word: parfum. Regulation (EC) 1223/2009 allows every fragrance composition and its raw materials to be named by this single word, so that a fragrance formula need not disclose each component.

But the collective word has an exception. The same clause requires the separate names of substances listed in the notes column of Annex III to be added. These are the fragrance allergens. When the content of such a substance in a product passes a set threshold, its name must appear, even though it sits inside the parfum.

That is why the words Limonene, Linalool, Citral, Geraniol, Eugenol often stand after parfum, on the last line. They are not separately added ingredients. In most cases they are part of the fragrance itself, named separately so that those who need to know can read them.

The line is small, but its reason is written out plainly. The recitals of the 2023 regulation describe contact allergy as a lifelong change in the way the body reacts to a specific substance. A person already sensitised may react at a concentration much lower than the one that first caused sensitisation. The same text estimates the share of the EU population allergic to fragrance allergens at about 1 to 9 percent.

From 26 substances to a new list

The old list is usually called the 26 fragrance allergens: linalool, limonene, citral, eugenol, geraniol, citronellol, coumarin and others, along with the two extracts of oakmoss and treemoss. When Regulation (EU) 2023/1545 was adopted on 26 July 2023, its own text recorded that 24 fragrance allergens in entries 45 and 67 to 92 of Annex III then had to be named individually.

The basis for the new list is an opinion of the Scientific Committee on Consumer Safety (SCCS), adopted at its plenary meeting of 26 and 27 June 2012. The SCCS confirmed that the existing substances were still relevant, and identified 56 additional fragrance allergens that had clearly caused allergies in humans and had no individual labelling requirement. Regulation 2023/1545 brings those 56 into Annex III.

The new list holds both single molecules and whole essential oils. Among molecules: carvone, menthol, anethole, linalyl acetate, vanillin. Among oils and extracts, the text names lemon oil (Citrus limon), lavender (Lavandula angustifolia) and lavandin (Lavandula hybrida), peppermint (Mentha piperita), eucalyptus (Eucalyptus globulus), ylang ylang (Cananga odorata), lemongrass (Cymbopogon), Damask rose, geranium, patchouli, sandalwood (Santalum album), clove leaf, cassia leaf.

The text also groups some substances under one name. Geranial and neral are labelled together as Citral. The two enantiomers of limonene and the racemic dipentene are labelled together as Limonene. One more point sits in the recitals: substances that can turn into known contact allergens through air oxidation or through metabolism in the body are to be regarded as equivalent to fragrance allergens and are subject to the same requirements.

Labelling thresholds for rinse-off and leave-on products

The thresholds are unchanged from the old list. An allergen must be named when its content exceeds 0.001 percent in a product that stays on the skin, and 0.01 percent in a product that is rinsed off. In more familiar units that is 10 ppm and 100 ppm. Leave-on products include creams, body oils, perfumes; rinse-off products include soap, shampoo, shower gel.

The two thresholds differ tenfold because contact time differs. A layer of body oil stays on skin for hours; soap lather stays for a few tens of seconds before water carries it away. The labelling threshold is a threshold for information, not a limit on use. A substance may be present at many times the threshold and still be lawful, as long as its name is listed and any separate limits that apply are respected.

The transition dates are written in the annex. Products that do not meet the new requirement may be placed on the EU market only until 31 July 2026, and may continue to be made available only until 31 July 2028. The recitals explain those three and five years by the large number of new allergens to be named and the large number of products concerned. At the time of writing, the first date has passed.

The annex adds one more condition for some substances that oxidise easily. Limonene must have a peroxide value below 20 mmol per litre. Some conifer oils and turpentine in the list carry a stricter requirement, below 10 mmol per litre. This condition is aimed at the quality of the material at the time of use, not only at its name.

Linalool and limonene in essential oils

The substances on the list are not foreign things added to essential oils. They are the essential oils. Limonene makes up 57 to 76 percent of cold pressed lemon oil. Linalool makes up 59 to 88 percent of coriander seed oil and more than half of linalool chemotype basil. Eugenol is the main constituent of clove, cinnamon leaf and pimenta.

One calculation shows why almost every product with a citrus oil lists Limonene. A body oil with 2 percent lemon oil contains roughly 1.1 to 1.5 percent limonene. That figure is more than a thousand times the 0.001 percent leave-on threshold. The same bottle holds geranial and neral, the two forms of citral, together about 0.9 to 6.3 percent of lemon oil; in the body oil, citral is still above the threshold.

Under the new regulation, lemon oil itself has its own name in Annex III. A leave-on product with lemon oil above the threshold will list Citrus Limon Peel Oil, then Limonene, Citral, and any other substance present above the threshold. A longer label does not mean the product has changed; it only says more about what was already in the bottle.

When the content of a substance is counted, the law counts the actual content in the product, whether it comes from a synthetic molecule or from an essential oil. One extract page in the library records the practical method: listed constituents are counted from the actual content of each lot. Lemon oil from two different harvests can give two different labels on the last line.

Oxidation raises allergenic potential

An opened bottle of essential oil is a slow chemical reaction. Oxygen in the bottle's headspace meets terpene molecules and over time forms hydroperoxides, epoxides, new alcohols and ketones. Pure limonene is rated as low concern; oxidised limonene is another matter.

The data on the library's limonene page put figures on that difference. At 1 to 3 percent, fresh limonene caused allergic reactions in 0 to 0.56 percent of the thousands of dermatitis patients tested. Oxidised limonene at 3 percent caused reactions in 0.9 to 2.8 percent. Combined data suggest oxidation may raise allergenic potential about tenfold. The hydroperoxides are the main cause.

The library's safety page adds a figure on speed. After twelve months at room temperature in an opened bottle, the monoterpene content of lemon oil can fall from 97 percent to below 31 percent; what disappears turns into oxidation products. Linalool oxidises in a similar way, and its page recommends adding 0.1 percent BHT or tocopherol and keeping the peroxide value below 20 mmol per litre.

This explains why the new regulation regards substances that can turn into allergens through oxidation as equivalent to allergens, and why limonene carries a peroxide limit. The label names the substance; storage decides what form that substance is in. Dark glass, a tight cap, a cool place and quick turnover are work that no line on a label can do instead.

Reading the label of a lemon oil

A bottle of cold pressed lemon oil carries three layers of information, each answering a different question. The botanical name and part, Citrus limon, fruit peel, cold pressed, say what the bottle is. The allergen list says which substances a person already sensitised should watch for. The dilution and storage guidance says how the bottle should be used.

Reading the second layer calls for the right attitude. The word Limonene on a label is not a warning that the product is dangerous. The recitals of the 2023 regulation call naming a measure of secondary prevention: information so that people already allergic to a particular substance can avoid it. For most users the line asks nothing. For a few, it is the most important line on the bottle.

The third layer belongs to the user. Cold pressed lemon oil also carries furocoumarins, bergapten among them, so it has its own threshold for light sensitivity when applied to skin exposed to the sun. That is another matter, not part of the allergen list, and it has its own page in the library. The allergen label answers one question; it does not stand in for the others.

The fragrance industry's standard, IFRA, runs alongside EU law but does not coincide with it. The essay One Set of Standards for Every Bottle explains where the two differ, and the essay on the INCI ingredient list goes further into the lines above the word parfum.

The names at the end of the list are not new.

They were already in lemon peel, in coriander seed, in clove buds.

The law only asks that they be called by name.