PEG-40 Hydrogenated Castor Oil

PEG-40 Hydrogenated Castor Oil is a surfactant. The European CosIng database assigns it two functions: emulsifying and cleansing. In practice, it helps keep oily components and fragrance dispersed in a predominantly water-based formula, allowing a clear product such as toner to contain an oily fraction without becoming cloudy.

The number 40 helps explain which form of the ingredient you are looking at.

Water, oil and fragrance in one bottle

Left alone, water and oil separate. Toner, micellar water and fluid lotion are formulas in which water is by far the main component, yet they still need to incorporate substances with little affinity for it: an oily fraction, an extract in a solvent or fragrance.

The surfactant makes that combination possible. One part has an affinity for water and another for oil, helping bring them together. This explains its role in clear products: when the oily components are dispersed at a scale far below visible-light wavelengths, light can pass with little scattering. The final clarity still depends on the complete formulation.

What the 40 means

CosIng's chemical description is hydrogenated, ethoxylated castor oil (Ricinus communis), with an average molar ratio of 40 moles of ethylene oxide.

The key word is average. The 40 describes the mean of a population of molecules; chain length varies from molecule to molecule. PEG-40 therefore gives the average of a distribution, with the approximation that entails.

For label readers, there is a practical consequence. PEG-6, PEG-40 and PEG-60 Hydrogenated Castor Oil share CAS number 61788-85-0. In this family, the CAS number remains the same as the degree of ethoxylation changes. That degree appears only in the INCI name's number: the three CosIng entries differ in moles, 6, 40 or 60, while the other listed details, including functions, coincide. On the label, the number distinguishes them.

Why 'hydrogenated' matters

CosIng lists PEG-40 Castor Oil separately, with its own CAS number, 61791-12-6, and a description of ethoxylated castor oil without the hydrogenation step. INCI names differing by one word can identify separately registered substances.

The starting material matters too. Unmodified castor oil, labelled Ricinus Communis Seed Oil, has CAS number 8001-79-4 and different CosIng functions: perfuming and skin conditioning. 'Castor oil' within an INCI name tells you the starting point. Behaviour in the formula then depends on the transformation the oil has undergone.

What the PEG prefix tells you

PEG indicates how the ingredient was made: a reaction with ethylene oxide called ethoxylation. Ethylene oxide appears in Annex II to Regulation (EC) 1223/2009 under reference 182. The same annex includes 1,4-dioxane, CAS 123-91-1, a possible by-product of that reaction. Annex II lists substances prohibited in cosmetic products, meaning they cannot intentionally be used as ingredients.

Traces left by industrial processing have separate rules. Article 17 permits unintended small quantities of a prohibited substance under its stated conditions and subject to compliance with Article 3, titled Safety. The Scientific Committee on Consumer Safety addressed 1,4-dioxane in Opinion SCCS/1570/15 of 15 December 2015, identifying 10 ppm in the finished product as a safe trace level for consumers.

PEG-related questions therefore belong in a specific context: good manufacturing practice, with a published rule and a stated trace level.

What European law says about this ingredient

PEG-40 Hydrogenated Castor Oil does not appear among prohibited or restricted substances in the annexes to Regulation (EC) 1223/2009.

The annexes do not set an ingredient-specific maximum concentration, exclude product categories or require a label warning for this entry. Such specific provisions accompany listed ingredients, and this one is not listed. This describes its regulatory classification; it does not replace assessment of the finished product.

Regulatory classification concerns how an ingredient may be used; it cannot predict how an individual’s skin will respond.

Where to find it on the label

It appears under its full name, PEG-40 Hydrogenated Castor Oil, including the number. Position reflects quantity only above 1%; below that threshold, order is flexible, so position alone says little.

The 1% threshold is explained in more detail in how to read an INCI list. For a whole label, use the INCI analyser.

Sources: CosIng, European Commission, entries for PEG-40 Hydrogenated Castor Oil, PEG-40 Castor Oil, PEG-6 and PEG-60 Hydrogenated Castor Oil, and Ricinus Communis Seed Oil. Opinion SCCS/1570/15 of 15 December 2015. Regulation (EC) 1223/2009, Annex II and Articles 3 and 17.