Replacement of synthetic ingredients with natural ingredients is not as simple as removal of each material one by one and substituting it, as Alchemy Ingredients explains in depth.

Over the past 50 years, there has been a gradual trend in the cosmetic industry to replace synthetic raw materials with more naturally derived, plant-based versions. In 1970, the approximate percentage of naturally-derived material (excluding water) in a typical cosmetic product was probably 50%, which included some animal derived feedstock.

In 2020, it was more likely to be 75% and this was wholly plant based. There are several drivers for this trend.

• Consumer perception that natural ingredients are healthier for the skin and hair.
• Concern about petrochemical-derived feedstocks and sustainability.
• Green manufacturing processes and plant based raw materials becoming readily available.
• Biodegradability concerns.
• Cosmetics formulators preferring to use natural raw materials.
• Label reading by consumers and not wanting ‘chemicals’ in their cosmetic products.

Limitations using natural materials

Performance

Often the natural raw material cannot be used as a direct 1:1 weight for weight replacement. This is because synthetic raw materials have usually been created specifically for a purpose, for example the viscosity modifier carbomer. This material was designed from scratch to bind and hold a great deal of water and provide a smooth, suspending, transparent gel.

Natural thickeners do not have that advantage as they are produced and extracted from plants or fermentation and are complex mixtures. Although transparent and smooth textures can be obtained, usually a much higher percentage of the thickener is needed to produce the same viscosity, for example a viscosity of 30,000Cps can be obtained with 0.2% of carbomer, whereas 2% of xanthan gum is required to reach the same viscosity.

Often the natural raw material needs to be taken into careful consideration due to special properties the material has, for example a particular pH or salt level requirements.

Predictability

One of the advantages of using synthetic materials is the predictability and reliability of these materials. They are often chemically pure (one single chemical substance), are often colourless and stable, and do not vary from batch to batch. When natural raw materials are used, the opposite is often true — the colour can be darker and can vary from batch to batch.

Due to the complex nature of natural raw materials, the performance of the product can vary depending on the formulation it is in. This is particularly true of preservatives, where the type of formulation, packaging and pH can greatly affect the level of natural preservative required.

Price

It is an unfortunate fact for natural cosmetic companies that natural raw materials are often more expensive in a formulation than the synthetic equivalent. There are several reasons for this: firstly, the starting raw materials are commonly farmed and this involves higher labour and energy costs than synthetic starting materials, which are usually petrochemical in origin.

Secondly, the extraction and refining processes required to make the material suitable for cosmetic use are often complex and expensive, pushing the cost up. Finally, the pricing for natural, premium raw materials can be set artificially high as it is known that these type of finished cosmetics are more expensive than standard ones.

Categories of natural ingredients that can replace synthetics

In the example categories listed below, the degree of difficulty in replacing synthetics is discussed. For some products, a simple substitution or careful selection is required without much effort or reformulation, in others a complete workaround is needed.

Emulsifiers

This is a relatively easy category of ingredient to replace with a natural alternative depending on the type of formulation being made. The main function of an emulsifier is to form a physical barrier between the oil and water phases, organise the internal phase (either droplets or liquid crystal type arrangements) and provide texture and body to the emulsion.

The earliest types of emulsifiers were in fact natural, for example egg, plants such as soapwort or hemp, soap, and mustard. In the 1940s and 1950s, synthetic emulsifiers were extensively developed, with ethoxylated (PEG based) materials becoming very popular due to their low cost and high functionality.

It was then that the concept of the HLB (hydrophilic-lipophilic balance) was introduced by Griffin, providing a simple classification system for emulsifiers to predict the type of emulsion formed and the behaviour of the emulsifier.

It is important to note that this system is only applicable to synthetic emulsifiers. It cannot be applied to natural emulsifiers easily because the hydrophilic and lipophilic groups are not as ‘pure’ and therefore the value is not accurate, and usually the emulsifiers are complex mixtures.

However, it has been successfully carried over to some emulsifier types such as the polyglycerol ester group of products, due to the similarity of the polyglycerol group to PEG. Table 1 shows some emulsifier categories and the synthetics that they replace.

It is worth noting that some commonly used raw materials used alongside and often blended with synthetic emulsifiers are in fact natural and 100% plant derived. Examples of these are cetyl alcohol, cetearyl alcohol, stearic acid and glyceryl stearate. With some careful formulating these popular natural materials can be used alongside natural emulsifiers to obtain a great texture.

Water thickeners

One of the most common ingredient categories in cosmetics that is targeted for replacement with natural ingredients is rheology modifiers and thickeners. Carbomer, a polymer of acrylic acid, is a useful and highly functional raw material specifically developed for the cosmetic industry to improve the feel, stability, and viscosity of a wide variety of cosmetic formulations, for example, face creams, lotions, facial and body gels, hair gel, hand sanitiser and many more.

The INCI name for carbomer is usually listed as ‘Carbomer’ but close derivatives include Acrylates/C10-30 Alkyl Acrylate Crosspolymer and Acrylates Copolymer.

Most of them produce highly viscous, transparent gels in water at a low use level. The texture and skin feel of carbomer make it a difficult product to replace effectively with natural alternatives. The key to replacing carbomer effectively is defining what function it has in the selected formulation. If transparency is the key property, and the high viscosity and suspension characteristics are not that important, then products such as cellulose gum, transparent xanthan gum and sclerotium gum could be considered.

If a high viscosity is required but transparency is not important, for example in a cream formulation, then gums such as guar, tara and gellan could be considered. Table 2 shows some natural thickener systems based on the functional properties required.

Click to read the full tables.

Surfactants

The all-purpose surfactant Sodium Laureth Sulphate (SLES) has both natural and synthetic molecular parts and is often targeted for removal by formulators due to ethoxylation of the Lauryl group. There are other reasons for this, not just the synthetic aspect, but also because it is a known eye and skin irritant and may not be suitable for some applications.

SLES is a very effective and cheap ingredient and is not easy to replace due to its superior foam production and the fact it is salt thickened, meaning that any alternative system probably has to be thickened using another technique such as a natural gum, giving a less favourable – and more expensive – rheology.

The secondary amphoteric surfactant Cocamidopropylbetaine is less often targeted for removal, however it does contain synthetic entities so in very natural products is sometimes replaced with coco-betaine, which is 100% naturally derived.

Common natural replacements are shown in Table 3. It is worth mentioning that performance is usually compromised by substituting the synthetics and effective foaming and cleansing is difficult to achieve using only natural ingredients.

Emollients

Emollients is an easy category of ingredients to replace with natural alternatives and often natural oils and esters are the first choice for many formulators due to their sensory properties. Most vegetable oils will be classified as natural and COSMOS approved.

However, it is worth checking with the supplier how the oil was extracted, as some are hexane-extracted from the seed or nut – making them unsuitable for COSMOS approval. For true natural classification, oils should be cold pressed or CO2 extracted.

There are a huge number of vegetable derived esters available and these can be considered COSMOS natural due to esterification being a permitted chemical process reaction. Many different sensory characteristics can be obtained with esters, from very light and volatile to heavy and substantive depending on the chain length, degree of saturation and branching of the fatty acids that make up the ester.

The synthetic emollient group mainly consists of paraffin oil and derivatives such as petrolatum, synthetic emollient esters and silicones. Silicones are worth a special mention as they are quite difficult to replace, particularly in haircare applications. It is hard to reproduce the slippery feel, smoothing effect and spreadability of silicones, as is the high heat stability in applications such as heat protection spray or serum.

Hair conditioners that are silicone free sometimes lack the smoothing effectiveness of those containing silicones, although ‘silicone free’ is a popular claim for those consumers who believe build-up on hair to be a problem. Table 4 shows a selection of popular natural emollients and their properties.

Colours

Essential in cosmetics to add interest to a toiletry product, or as a decorative colour cosmetic, the use of colours in cosmetics has always been a challenge. In natural cosmetics, it is difficult to achieve the vibrancy and longevity of a synthetic colour and some compromises need to be made. However, natural colours can be used effectively in some cases.

Colours can be oil soluble, water soluble, or in the form of insoluble pigments. The water-soluble group of products include organic molecules such as blackcurrant extract (red/purple), which can colour a cream or other water based preparation. These form part of a group of molecules known as anthocyanins and other examples in this group include coloured potatoes, flowers and carrots.

Another common natural colourant is annetto, which contains bixin and norbixin, a yellow oil soluble colour. Other natural colours include chlorophyll (green), beta-carotene (orange), curcumin (yellow-orange) and betanin from beetroot (red/purple). Some of these compounds have a pH requirement and are more stable on the acidic side. Many do not claim to be fully light stable on a long term basis so caution is needed when using them.

In the natural pigments (insoluble) sector, compounds such as iron oxides (brown) and vegetable carbon (black) can be used, alongside coloured substances such as flower petals, crushed fruit and vegetables and peels. Many of these natural colours can be derived from the food industry, although in cosmetics the shelf life is normally longer, so colours need to be more light and pH stable.

Fragrances

This category is fairly easy to replace with natural alternatives, but care needs to be taken from a regulatory and safety point of view. Essential oils can be very effective fragrance oil substitutes, however the level of use in a final product and the advice for different types of products needs to be taken into account as they are potentially irritant and toxic raw materials, despite being natural.

As an example, wintergreen oil is toxic at fairly low levels, and cinnamon and clove can cause skin irritation. Another consideration when using essential oils is that they do not contain the carrier oils, solvents, stabilisers and other synthetic components of fragrance oils. This means that they may change over time in a cosmetic product, or even fade away easily.

However, there are many natural cosmetic products that successfully use essential oils as their fragrance component without the use of synthetic compounds, even though this is an expensive option.

Preservatives

A notoriously difficult category of materials to replace, the field of truly natural preservatives is small and not particularly effective. In order to replace broad spectrum preservative systems such as phenoxyethanol and ethylhexylglycerin, a blend of different natural ingredients need to be used.

One common way to improve the efficacy and reduce the amount of preservative required is to add humectants such as glycerine, 1,2 Propanediol or butylene glycol. This will reduce water activity as well as overall water percentage and help with natural preservation. Anhydrous or nearly anhydrous products could also be considered for the same reason.

If water-based preservatives are required, there are some natural choices available, for example Lactobacillus Ferment, which is a probiotic, although it does require an acidic or neutral pH to work. Other systems include variations on benzoic acid, benzyl alcohol, potassium sorbate and sodium benzoate, these are classed as natural systems even though they are synthetic.

Other extracts such as magnolia extract, grapefruit seed extract and naticide (INCI: Fragrance) can be used, although they are often most effective when combined with boosters such as caprylyl alcohol caprylic acid, gluconolactone or glyceryl caprylate.

Conclusion

Replacement of synthetic ingredients with natural ingredients is not as simple as removal of each material one by one and substituting it. Care needs to be taken to keep good stability and texture in order to produce a finished formulation that the consumer will accept and enjoy, even if it is more expensive.

It is anticipated that the trend for sustainable, plant based ingredients will continue, however with cost of living pressures, formulations still need to be affordable, putting pressure on material suppliers, brand owners and formulators. Clever, creative natural materials are out 
there – so get experimenting!