Total Limit & Allergen Sum Calculation in a Fragrance Formula

Most formulas contain more than one fragrance oil. Two or three different fragrance oils, a handful of essential oils, perhaps an accord (a cohesive scent blend built from several raw materials) — all sitting side by side. That is precisely where the problem begins. The same restricted molecule can arrive simultaneously from more than one raw material. You check each one individually, and every single entry looks clean. Yet the combined total has already exceeded the limit.

IFRA limits apply not to the label of the fragrance oil but to each individual substance present in the finished product. The logic of the calculation is therefore straightforward, even if it is easy to overlook: add up the amounts of the same substance coming from all sources, then compare the total against the limit.

First, let us clarify a key distinction. The IFRA Standard draws the upper safe-use boundary for a given substance. Allergen disclosure, on the other hand, is an entirely separate matter: it is a labelling obligation under the EU Cosmetics Regulation. Industry sources make this explicit: IFRA Certificates do not replace EU allergen labelling calculations. Both must be assessed independently. Just as the top note hands the stage over to the base note once it has faded, labelling responsibility takes over once IFRA safety compliance has been established. A manufacturer who conflates the two will create gaps in the field.

The true concentration of an allergen in the finished product is the sum of contributions from all raw materials that contain it. Looking at a single fragrance oil and declaring it "below the threshold" is the most common mistake. Linalool is present in bergamot, in lavender, and inside a synthetic accord. If all three are on the bench at the same time, the combined total will exceed the limit.

The essence of the calculation is simple. Using supplier data, multiply the concentration of each allergen in a given fragrance oil or raw material by that material's percentage in the finished formula. Compare the resulting figure against the allergen thresholds.

The EU notification thresholds are clear and confirmed by current sources: allergens must be declared when they are present at or above 0.001% (10 ppm) in leave-on products (such as perfume and eau de parfum) and at or above 0.01% (100 ppm) in rinse-off products (such as shower gel and shampoo).

There is one further critical point. These allergens are not confined to synthetic materials. Fragrance allergens are not limited to synthetic compounds; many occur naturally in botanical raw materials. Essential oils and plant-based extracts may contain allergenic substances subject to the same labelling requirements. In other words, the assumption that "I used naturals, so there are no allergens" is incorrect. Some of the most heavily restricted substances (Citral, Eugenol, oakmoss and the like) are often present at the highest levels in natural essential oils. Safety depends not on the source but on the molecule and its usage level.

Do you see the issue? None of the individual entries looks alarming. Yet the combined total comes to 1.78% — far above the leave-on threshold of 0.001%. This Linalool must be declared by name on the label. Moreover, for some substances this is not only a labelling matter but also an IFRA safety limit; check both separately.

The IFRA calculation rests on two pillars: selecting the correct category and adding up every source of the same substance. If the category is wrong, even the most meticulous summation is worthless.

Why is the category so decisive? Because the limit varies according to exposure intensity. IFRA divides scented products into categories based on exposure intensity. Each category reflects differences in contact duration, skin area, frequency of use, and whether the product is rinsed off or remains on skin. The effect can be striking: because exposure varies so greatly across categories, the same substance may be permitted up to 5% in a rinse-off product while being restricted to 0.1% in a leave-on formulation. The fragrance load must therefore be calculated relative to the product type. For category selection, the Esans Akademi article "IFRA Category Selection: Is 4A, 5A or 5B Right for Your Product?" provides step-by-step guidance.

IFRA establishes these limits through QRA (Quantitative Risk Assessment). This model combines toxicological thresholds with real-world consumer usage patterns to derive maximum safe exposure levels.

The summation logic is identical to that used for allergens: the total concentration of a restricted substance (such as Citral) in the finished product is the sum of contributions from all fragrance oils that contain it. This total must not exceed the IFRA limit set for that substance in the category you have selected.

Regulations do not stand still. A calculation performed without knowing today's current figures may be invalid by tomorrow. Two recent developments directly affect summation calculations.

The first concerns IFRA. The 51st Amendment added 59 new rules to the IFRA Standards, bringing the total to 263. It was officially published on 30 June 2023. The transition period has also expired: perfume brands and cosmetic companies with formulas containing fragrance oils and/or essential oils had until the end of October 2025 to bring those formulas into compliance with the revised IFRA Standards. Full compliance is therefore expected as of today.

One detail directly affects category calculations: reed diffusers and similar products were moved to Category 10A due to concerns about exposure during use. If the category has changed, assume the limits for that product have changed too, and recalculate.

The second concerns EU allergens. The list of allergens subject to disclosure has been substantially expanded. The EU, through Regulation (EU) 2023/1545, extended fragrance allergen disclosure requirements and amended Annex III of the Cosmetics Regulation. This update increased the number of individually declarable fragrance allergens from 26 to over 80. The thresholds have not changed — but you now need to sum far more molecules. If you are still working from the old list of 26, your calculation is incomplete.

Even when the calculation is set up correctly, manufacturers often stumble on units and the question of responsibility. Let us close off a few traps.

The unit trap: grams or millilitres? Building your formula on a gram (g) basis is the most reliable approach, because weighing is precise. However, do not forget density when converting to volume. Citrus oils are light (specific gravity ≈ 0.84), whereas heavy resins and some synthetics are denser than water (>1.10). The same 100 g occupies approximately 119 ml in a citrus oil and around 90 ml in a heavy synthetic. If you fail to include density in your ml↔g conversion, you will end up with overflow or underfill at the bottling stage. Always calculate allergen percentages by weight — the thresholds are mass-based.

The natural-versus-synthetic fallacy. The assumption that "natural is safe, synthetic is risky" is incorrect and creates legal exposure. Natural bergamot is phototoxic (it can cause skin discolouration in sunlight); oakmoss is among the most heavily restricted allergens. By contrast, some pure synthetics are almost entirely safe from an allergenic standpoint. Do not overlook natural oils in the summation — many allergens originate there.

Keep responsibility and process separate. In Turkey, cosmetic product notification and the obligations of the responsible person are distinct matters; the notification steps (process) and the legal liability of the manufacturer or responsible person must not be conflated. Every cosmetic product placed on the EU market must have its own safety report; each unique fragrance composition counts as a separate product. And remember: a cosmetic/perfume fragrance oil is not a food product; it is not edible or drinkable. Never confuse a food flavouring with a cosmetic fragrance oil.