In her SPC/SCS prize winning essay Belinda Pilmore provided best estimates for the % by weight of the individual ingredients found in skin moisturisation and reformulated a classic product in line with natural trends
Ingredients are incorporated in a cosmetic formulation based on the function they perform within the product. The role each ingredient plays in combination with or in isolation from other ingredients provides valuable clues as to its approximate input in the formulation.
Provided with a list of ingredients, it is possible to determine approximate input % for a finished product. Examining the various functions of cosmetic ingredients in a lotion and considering European labelling rules for cosmetic products, then using the HLB system, a structured step-by-step approach and various raw material suppliers instruction booklets it is possible to provide best estimates for the % by weight of the individual ingredients found in a product.
This paper looks at a current formulation and following the determination of the approximate inputs of all ingredients, provides a label description aimed at selling the product to a consumer. But given current, natural trends and what consumers now look for in their personal care products, it is also possible to reformulate, still allowing strong moisturising claims but avoiding ingredients that are no longer perceived as appealing to customers.
The European Commission requires that ingredients be listed using a standardised INCI name (International Nomenclature of Cosmetic Ingredients) in descending order of weight when included at or above 1%. Below 1%, ingredients can be listed in any order, with colours to be listed at the end (EC Cosmetics Directive Article 6).
Analysing the current formulation:
l Determine emulsion type - The first, and therefore predominant ingredient is aqua; most likely forming the continuous phase in an oil-in-water emulsion. Additionally, Bancroft’s rule states ‘the phase in which the emulsifying agent is the more soluble tends to be the dispersion medium’ (Shaw, 2003). Three of the four emulsifiers used in this lotion are more hydrophilic (water loving), and favour the formation of an oil-in-water emulsion. It would therefore be an oil-in-water emulsion.
l Estimate HLB value - While not a fool proof approach to determining the composition of an emulsion, the HLB system (hydrophilic-lipophilic balance) does provide approximate input of emulsifying agents, and subsequent lipid phase ingredients, as a guide before trial and error testing (Schott, IFSCC 1997; and Shaw, 2003). Since oil-in-water emulsions form when the HLB values of the emulsifiers are between 8 and 15 (Shaw, 2003), we will assume this formulation to fall somewhere in the middle, approximately 11.
l Estimate emulsifying agent inputs - Minimum input information provides a guide for further calculations: cetyl alcohol, 2% (Croda, 2006; Cognis, 2006); stearic acid, 0.5% (Cognis, 2006); and steareth-100, 0.5% (Uniqema, 2006). Where not provided, as in the case of glyceryl hydroxystearate, an approximate input % can be calculated using the following formula:
HLB = (% input of cetyl alcohol as part of total emulsifiers x HLB cetyl alcohol) + (% input of glyceryl hydroxystearate as part of total emulsifiers x HLB glyceryl hydroxystearate) + (% input of stearic acid as part of total emulsifiers x HLB stearic acid) + (% input of steareth-100 as part of total emulsifiers x HLB stearic acid).
Then, by trial and error, and knowing the approximate HLB value: (0.42 x15) + (0.38 x 3.4) + (0.1 x 15) + (0.1 x 18.8) = 10.972.
Lastly, converting this back to % input: cetyl alcohol = 0.42 of emulsifiers at 2%, thus 0.38 glyceryl hydroxystearate is approximately equal to an input of 1.8%.
l Estimate lipid input - All emollient and occlusive skin conditioning agents used in this formulation make up the lipid phase. Based on the HLB value of approximately 11, the formulation outlined above and a few trial and error calculations, the approximate inputs of each would be: HLB = (0.435 x12) + (0.304 x10) + (0.174 x 8) + (0.043 x 9) + (0.043 x 7.5) = 10.362.
l Estimate hydrophilic ingredient input - The third ingredient is a hydrophilic ingredient, glycerin, used as a humectant and solvent. Its input level can vary from 0.5-20% (Croda, 2006). However, since the cetyl palmitate can only be input up to 5% (Croda, 2006), the glycerin can only be included up to 5% too. Paraffinum liquidum (the next listed ingredient) is estimated to be added at 3.5% and it is therefore possible to approximate the glycerine input at 5%.
l Estimate preservative input - The preservatives in this formulation are DMDM hydantoin and iodopropynyl butylcarbamate. Assuming that the preservatives were used at around the midpoint of their suggested input value to reduce possible sensitivity reactions while still maintaining efficacy, the DMDM hydantoin would have been added at 0.3% and iodopropynyl butylcarbamate at 0.15%.
l Estimate remaining ingredient input - Fragrances are the most likely cause of allergies (Goossens, in Paye, Barel & Maibach, 2006) so are added at small amounts. Smelling the product would enable us to determine a possible strength of addition, but an estimate would be 0.3%.
Carbomer is a very potent thickening and emulsion stabilising agent, particularly in the presence of a neutraliser such as potassium hydroxide. Since other emulsion stabilisers and thickeners are in this product, the addition of carbomer would be low at around 0.2% and the potassium hydroxide would be added at this same % to fully neutralise the carbomer.
Acrylates/C10-30 Alkyl Acrylate Crosspolymer is another polymeric thickening agent and as part of this formulation would also be added at a very low level (approximately 0.2%).
Tetrasodium EDTA is added as a chelating agent and since this product is not going to be coming into contact with water, as opposed to a bath gel, its input would be low (approximately 0.05%).
Red 4 is a colouring agent. A very strong colour, when added to this product (a white base) a little colour would go a long way. As the finished product in this case is most likely a pale pink colour, a very small amount of dye would be used (approximately 0.05%).
Aqua makes up the remainder of this formula, so now it is a matter of subtracting all other ingredient inputs from 100% to estimate the input of aqua in this product. Any adjustments to pH may be achieved through an as needed (qs) input of potassium hydroxide, as this is already present in the formula to neutralise the carbomer.
Label claims for the current product read as follows: “Revitalise the appearance of your skin with the intense moisturising benefits of this decadently rich moisturising lotion. Designed to protect moisture levels in skin exposed to drying environmental conditions, this luxuriously soft formula seals in hydration for a softer, more supple looking appearance. Reverse the visible signs of ageing by replenishing the moisture your skin craves - and lock it in - with the moisture protective barrier formed by regular application of this nurturing lotion.”
Consumer perception & ingredients:
Consumers are increasingly choosing products based on their content of certain natural ingredients (eg plant oils), and avoidance of certain synthetic ingredients such as SLS and parabens (Woodruff, 2006; Datamonitor, 2007; Olioso, 2006; Caldwell, 2006). Barbara Olioso suggests this trend towards choosing more natural comes in part from the association of natural with purity and the bad press associated with using the aforementioned synthetic ingredients. She suggests that regardless of whether the press was true, consumers have now lost trust in using products containing these ingredients and are reluctant to change their opinion. Georgina Caldwell identifies two key motivating factors influencing consumers to change their purchases toward natural: firstly concern about the chemicals their personal care products contain based on their skin’s reaction and secondly the desire for quality; natural products being perceived as superior to many conventional offerings.
Datamonitor explains succinctly several reasons for the possible shift in consumer trends:
- more concern over what is used on their skin today than ever before
- preference for natural ingredients with active plant constituents
- avoidance of synthetic ingredients, perceived to be harsh
- emphasis on what is consumed internally translating to concern about what is being applied externally
- perceived benefits from using vitamins and bioactive compounds while avoiding other ingredients
- widespread perception that natural is safer and therefore better for long-term health
- natural perceived as healthier, providing additional emotional benefits when using the product
- today’s un-naturally fast paced lifestyles resulting in some consumers reverting to more natural products to establish perceived balance in their life
Reformulating process:
When reformulating, choosing more natural ingredients was clearly most important. For this reason, the lipid ingredients were replaced with natural and exotic sounding oils rich in natural vitamins. Tocopherol was added, the dimethicone and colour was removed, the carbomer and acrylates replaced by xanthan gum as an emulsion stabiliser, the preservatives changed from purely synthetic to those perceived to have been derived from natural sources originally and the fragrance was removed in favour of essential oils. The same emulsifying base was used in the new formulation, and in the absence of knowing HLB values for the exotic and essential oils, a total of 11.5% of combined oil content (including vitamin E and essential oils) was used. This input was based on the previous formulation’s combination of emulsifiers and lipid input; and the author’s personal industry experience.
When writing the ingredient panel, all ingredients with an input less than 1% were listed based on consumer acceptance and marketability, with all botanical ingredients listed before the preservatives and chemical-sounding names.
The improvements made allow the label claim for the new product to read as follows:
“Exotically enticing and intensely hydrating, this elegant lotion gives your skin a kiss of nature with plant and essential oils. Enriched with borage oil, a natural source of gamma-linoleic acid, to moisturise, condition and restore the vibrant appearance of your skin; Bertholletia excelsa, a naturally rich source of antioxidant vitamins A and E; and hydrolysed elastin, to promote tone and elasticity for supple looking skin. Light to apply, this decadent lotion absorbs rapidly forming a moisture protective barrier against trans-epidermal water loss, leaving your skin feeling luxuriously soft and deeply moisturised.”
The varying functions of cosmetic ingredients determine their input in a product. Some may be used for a technological function while others, such as plant extracts or essential oils, may be added to suit consumer trends and requirements. With the turn towards more natural products, consumers have become more ingredient aware and formulations have had to adapt with the times.