A 709 page document, the January 2024 edition, holding the IFRA Standards up to and including the 51st Amendment. Each page is one substance or group of substances, and under the name sits a table of twelve product categories with twelve figures. This essay reads one such page from the top down.
A table of figures for each substance
The page on citral opens with the CAS number, 5392-40-5, along with the numbers for geranial and neral. Next come the synonyms, the publication history, then two implementation dates. After that a line in capitals: recommendation, restriction. And last, the table of maximum acceptable concentrations in the finished product, in percent.
The table reads like this. Category 1, lip products, 0.11 percent. Category 4, fine fragrance, 0.60 percent. Category 5A, body lotion, 0.15 percent. Category 9, rinse-off products such as soap, 1.2 percent. Category 12, products not in contact with skin, no restriction. One molecule, twelve figures, depending on where it will go.
IFRA is the International Fragrance Association, the international body of the fragrance industry, with headquarters in Geneva and operations in Brussels. The IFRA Standards are the industry's own set of rules: member companies commit to comply, and some countries reference them in their law. The standards are updated through numbered amendments.
The 51st Amendment, often shortened to IFRA 51, was notified on 30 June 2023. It does not replace the whole set; it adds new standards and revises some older ones. In the consolidated document each page states which amendment the standard belongs to. The citral page says Amendment 49, 2020. The methyl eugenol page says Amendment 51, 2023.
IFRA and RIFM
A figure in the IFRA table is not set by IFRA alone. It comes out of a chain of assessment that starts at another body: RIFM, the Research Institute for Fragrance Materials, a non-profit scientific organisation founded in 1966. RIFM gathers and assesses safety data on fragrance ingredients and provides the science behind the standards.
Each standard page has a section recording the conclusion of the Expert Panel for Fragrance Safety. The panel reviews all available data on the substance and recommends concentrations for the twelve product categories. The page also names the property driving risk management: for citral, dermal sensitisation and systemic toxicity; for oakmoss extracts, dermal sensitisation alone.
For skin sensitisation, the method since the 49th Amendment of 2020 is quantitative risk assessment, known as QRA2. Its starting point is the NESIL, the dose per unit area of skin at which a substance is not expected to induce sensitisation. From there, a limit for each product category is derived from the amount of product used, the skin area in contact, and the total exposure from all products used daily.
So when several assessments give several limits, the IFRA table keeps the lowest figure for each category. The standard page says so plainly: the maximum acceptable concentration is the lowest level obtained per category when the endpoints are compared.
Product categories 1 to 12
A substance meets skin in very different ways depending on the product. Lipstick may be swallowed in small amounts. Perfume is sprayed on a small area and stays for hours. Lotion covers the whole body. Soap stays on skin for a few tens of seconds. A scented candle does not touch skin at all. The twelve IFRA product categories are a way of dividing those differences into boxes that can be calculated.
The twelve category system has been used since the 49th Amendment, replacing the eleven categories before it. Some categories split into subcategories: 5A to 5D, 7A and 7B, 10A and 10B, 11A and 11B. The easiest examples to remember are Category 1 for lip products, Category 4 for fine fragrance, Category 5A for body lotion, Category 9 for rinse-off products such as soap, Category 12 for products not in contact with skin such as candles and air fresheners.
The gap between categories can be wide. For methyl eugenol, the 51st Amendment gives 0.011 percent for Category 4, 0.0015 percent for Category 5A, only 0.00021 percent for Category 5B, and 0.066 percent for Category 12. For the same substance, the limit in fine fragrance is about seven times the limit in body lotion. The reason is not the substance but its use: lotion covers a much larger area of skin.
For a single fragrance mixture intended for several categories, the standard requires the strictest limit to apply. A formula used both for a perfume and for a lotion must be calculated to the lotion's category, unless the two versions are calculated separately.
Prohibition, restriction and specification
Each IFRA Standard takes one of three forms, sometimes more than one. Prohibition: the material should not be used as a fragrance ingredient. Restriction of use: the material should be used only in the quantity stated in the standard. Specification: the material should be used only if it meets the criteria stated in the standard.
Safrole is an old example of prohibition. The standard on safrole, isosafrole and dihydrosafrole was published in 1987, under Amendment 17, with an earlier publication in 1976. These substances should not be used as fragrance ingredients, and natural extracts containing them should not be used as substitutes. Safrole coming from natural essential oils is accepted as long as the total concentration in the finished product does not exceed 0.01 percent.
Methyl eugenol is an example of restriction. It occurs naturally in small amounts in many essential oils, and the limits quoted above apply to the total in the product, including the part that comes from oils. The standard page has a section on contributions from other sources, pointing to an annex that lists typical natural levels.
Oakmoss extracts carry two forms: restriction and specification. The restriction is 0.10 percent for Category 4 and 0.076 percent for Category 5A. The specification is that atranol and chloroatranol each stay below 100 ppm in the extract, that dehydroabietic acid not exceed 0.1 percent, and that no treemoss be added. The standard notes that these levels have not been raised since their publication in Amendment 43 of 2008, because they are tied directly to the amount of atranol and chloroatranol in the product. The essay Oakmoss · A Lichen on the Bark tells the rest.
Where IFRA and EU law differ
The two systems look at the same bottle from two different places. IFRA is the industry's self-regulating standard, binding its members through commitment. EU cosmetics law, Regulation (EC) 1223/2009, is law directly applicable in every member state, and it applies to the finished product on sale.
EU law lists substances prohibited in cosmetics in Annex II and substances allowed only under conditions in Annex III. Substances classified as carcinogenic, mutagenic or toxic to reproduction in categories 1A and 1B are banned in cosmetics, save narrow exceptions. IFRA restricts by product category with twelve figures for each substance.
The clearest difference is in allergens. For citral, EU law requires the name on the label above 0.001 percent in leave-on products, but the citral entry in Annex III sets no maximum concentration. IFRA sets a maximum for each category, 0.60 percent in fine fragrance, 0.15 percent in body lotion, but says nothing about labels. One speaks to the person reading the label; the other speaks to the person writing the formula.
The timelines differ too. For standards published in the 51st Amendment, the implementation dates are 30 March 2024 for new creations and 30 October 2025 for existing creations. The standard states that these dates apply to the supply of fragrance mixtures, not to finished consumer products already on the market. EU law on allergen labelling has its own dates, 31 July 2026 and 31 July 2028, as the essay The Names at the End of the Ingredient List sets out.
The IFRA certificate of a blend
An essential oil blend is a mixture of many substances, and each oil in it is itself a mixture of many substances. To know how much of the blend can be used in a product, the contribution of each restricted substance has to be added up, from every oil that contains it. The result is recorded on an IFRA certificate: a document from the supplier for a given mixture, stating the maximum use level in each product category under a named amendment.
A hypothetical calculation shows the method. A blend holds 30 percent lemon oil; lemon oil contains geranial and neral, together up to about 6.3 percent at the high end. Citral in the blend can therefore reach about 1.9 percent. The Category 4 limit for citral is 0.60 percent, so the blend can be used at up to about 31 percent in a fine fragrance. The Category 5A limit is 0.15 percent, so in a body lotion the blend can be used at no more than about 7.9 percent.
In practice a blend holds several restricted substances at once, and the blend's maximum in each category is the level allowed by the strictest of them. The real content of each lot of oil varies, so a serious certificate is calculated from the lot's analysis, not from an average figure in a book.
A certificate does not say a blend is safe in every situation. It says that this blend, at a use level not above the figure given for this category, conforms to the standards of that amendment. Reading it correctly means reading three things together: the product category, the figure, and the amendment number.
One molecule, twelve figures.
The figure is not in the molecule.
It lies in the distance between the molecule and the skin.