Annex V, entry 29 of the EU Cosmetics Regulation sets a maximum phenoxyethanol concentration of 1.0% in the ready-for-use product. For a blend, its addition level must be multiplied by its phenoxyethanol content. Contributions from other ingredients are then included in the same total.

The entry identifies phenoxyethanol by CAS number 122-99-6, and ECHA lists it as a cosmetic preservative. Formulation calculations add the phenoxyethanol mass contributed by every ingredient, then divide by the total ready-for-use product mass. Ingredient quantity and composition determine each contribution.

How two blends contribute a combined 0.9%

Consider a hypothetical 100 kg finished batch. Adding 1 kg of a blend containing 80% phenoxyethanol contributes 0.8 kg of phenoxyethanol. The blend accounts for 1% of the finished product, while its phenoxyethanol accounts for 0.8%. The remaining blend mass consists of other components.

The same formula also includes 0.5 kg of another ingredient containing 20% phenoxyethanol. This contributes a further 0.1 kg. The two contributions total 0.9 kg; dividing by the 100 kg finished mass gives a phenoxyethanol concentration of 0.9%.

The two blends add 1.5 kg of material, containing 0.9 kg of phenoxyethanol. Their remaining components belong in the finished-product mass but not in the phenoxyethanol mass. The finished concentration in this example is therefore 0.9%, rather than the combined blend addition percentage.

The calculation sums each ingredient mass multiplied by its phenoxyethanol mass fraction, then divides by total finished-product mass. If additions are already expressed as finished-product mass percentages, each percentage is multiplied by the relevant phenoxyethanol fraction before summing. The 80% and 20% contents enter as 0.80 and 0.20; ingredient proportion and ingredient composition are separate factors.

Ingredient composition changes the remaining allowance

The example already contains 0.9% phenoxyethanol, leaving 0.1 percentage point below the 1.0% maximum. Adding 0.2 kg of pure phenoxyethanol, while reducing other ingredients to keep the finished batch at 100 kg, increases the total concentration to 1.1%. The direct addition joins the amounts already contributed by both blends.

Retaining the 0.2 kg direct addition in a 100 kg batch requires at least 0.1 kg less phenoxyethanol from the other ingredients. Reducing only the 80% blend means removing 0.1/0.80 = 0.125 kg of that material. Its addition falls from 1 kg to 0.875 kg, contributing 0.7 kg of phenoxyethanol. Together with 0.1 kg from the second blend and the 0.2 kg direct addition, the total becomes 1.0 kg. Other components containing no phenoxyethanol replace the removed blend mass.

Replacing a blend can change finished concentration even when its addition quantity stays constant. The replacement calculation uses its phenoxyethanol mass fraction and actual addition quantity. Together, these determine how much of the finished-product allowance that ingredient occupies.

Total batch mass also matters. The 1.1% calculation assumes that other components are reduced to preserve the 100 kg total. If finished-product mass changes, the denominator changes with it. The original total cannot be carried over into the calculation for a different batch composition.

Changing composition offers another route in this example. A first blend containing 70% rather than 80% phenoxyethanol contributes 0.1 kg less when its addition stays at 1 kg. Combined with the second blend and the 0.2 kg direct addition, finished concentration becomes 1.0%. Reducing blend quantity and reducing its phenoxyethanol fraction are two distinct formulation changes.