In this article about skincare products in cosmetic science you will learn about the skin’s epidermal structure (outermost layer of the skin), the different types of skincare preparations, skincare ingredients including niacinamide, peptides, ceramides and hydroxy acids – their formulation, regulation and claims. Keep on reading to find out more about skincare products.
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Skin Structure
Epidermis
Thickness: 180 μm.
Location: outermost layer of the skin, above the dermis.
Main Function: physical barrier to the external environment.
The epidermis is the outermost layer of the skin. Notably, this layer of the skin is non-viable (not alive) because the blood supply from the dermis does not reach here. Furthermore, the epidermis is in a constant state of renewal, with the formation of a new cell layer of keratinocytes at the stratum basale, and the loss of their nucleus and other organelles to form desiccated, proteinaceous corneocytes on their journey toward desquamation. As a result, cells produced in the stratum basale gradually push existing cells upward, moving them further away from the viable (live) layer, which eventually leads to their degradation and shedding from the skin’s surface. Additionally, the cells in this layer of the skin are held together by desmosomes, which interconnect the keratin of adjacent cells.
Stratum Corneum (Horny Layer)
Thickness: 20-30 cell layers.
The stratum corneum (SC) is what you see when you look at your skin. It is the primary barrier of the skin responsible for regulating trans-epidermal water loss (TEWL), keeping pathogens out, and molecular exchange.
This layer is made up of cells called “corneocytes,” which are approximately 50 μm in length but only 1.5 μm thick, making them very flat cells. Notably, corneocytes lack a nucleus and are composed of 70-80% keratin, making them similar to the scales we associate with lizards. Furthermore, corneocytes have a cornified cell envelope with a protein/lipid polymer structure that allows them to anchor intercellular lipids to the protein structures in the cornified envelope, providing structure and barrier function to the stratum corneum.
Additionally, these cells are suspended in an intercellular matrix made up of ceramides, free fatty acids, cholesterol, cholesterol esters, and cholesterol sulfates, with a notable absence of phospholipids. Specifically, ceramides are bonded sphingoid bases and fatty acids, categorized based on their polarity. Meanwhile, fatty acids are typically long-chained saturated acids. Moreover, cholesterol and cholesterol esters reduce the fluidity of intercellular lipid lamellae, thereby increasing the rigidity of the stratum corneum. Lastly, Natural Moisturizing Factors (NMFs) act as humectants and plasticizers, contributing to the overall hydration and flexibility of the skin.
Stratum Lucidum
This layer of the skin is only present on thick parts of the skin (for example: palms of your hands and soles of your feet). The stratum lucidum is so far from the viable (live) layer of the skin, that it loses cell nuclei and other organelles. Keratinisation increases (formation of keratin molecules) and the cells are compacted between the layers of skin, this creates flattened cell structure, similar to those found in the stratum corneum.
The palms of our hands and soles of our feet need these extra couple layers of skin to protect them from insults typically associated with limb extremities (holding, pushing, walking bare-foot).
Stratum Granulosum
Thickness: 3-5 cell layers.
In the stratum granulosum, intracellular keratohyalin granules and membrane-coating granules containing lamellar subunits arranged in parallel stacks are present, which are believed to be the precursors of the intercellular lipid lamellae of the stratum corneum. Moreover, this layer contains hydrolytic enzymes, including stratum corneum chymotryptic enzymes (SCCE) — a serine protease associated with desquamation. As the cells approach the upper layers of the stratum granulosum, the lamella granules are then extruded into the intercellular space.
Stratum Spinosum
In the stratum spinosum, structures change from columnar to polygonal. The cells in this layer still have all their organelles (including their nuclei), as they are close enough to the viable (live) layer of skin. These cells have an enlarged cytoplasm containing many organelles and filaments. The cells are not fully keratinised (unlike those in the stratum corneum), but they do contain keratin tonofilaments.
Stratum Basale (Germinativum)
Thickness: 1 cell layer.
The stratum basale (germinativum) is only one cell thick, These cells are called keratinocytes. These are the only cells which undergo cell division in the epidermis. All of the above mentioned cells originated through cell division in this layer, and eventually degrade as they move further away from this viable (life) layer of the skin. The stratum basale is the only layer in the epidermis which contains skin appendages, namely; merle cells, Langerhans cells and melanocytes.
The main function of the stratum basale is cell division. The stratum basale produces new cells every day. The life cycle from synthesis in the stratum basale to desquamation (shedding) from the stratum corneum is approximately 28 days. This means your skin totally renews itself every 28 days.
Epidermis Skin Cell Types
Corneocytes
Corneocytes are derivatives of keratinocytes. These cells are non-viable with no organelles. They are keratinised, flat and rigid. Corneocytes are found most notably in the stratum corneum, but undergo the process of cornification all the way from the stratum spinosum.
Keratinocytes
Keratinocytes are found in the stratum basale (germinativum) layer alone. They are the only cells in the epidermis which actively undergo cell division. These cells contain all their organelles and are one of the only cells which undergo molecular exchange with the deeper layers of the skin.
Langerhans Cells
Langerhans cells are dendritic cells (major antigen presenting cells in the skin). These cells are generated in the bone marrow. When activated by antigens, they migrate from the epidermis to the dermis and onto the regional lymph nodes where they initiate an immune response. They play a key role in allergic dermatitis.
Melanocytes
Melanocytes produce melanin, high molecular weight polymers that provide pigmentation to the skin, hair and eyes. Their function is to protect the skin against UV radiation. They absorb potentially harmful UV radiation and prevent these rays from damaging the sensitive structure below the epidermis. Melanocytes produce two forms of melanin: eumelanins (black-brown) and pheomelanins (yellow-red).
Merkel Cells
Merkel cells are associated with nerve endings. They are pressure sensitive and able to sense changes in our environment. These cells are concentrated in touch sensitive areas such as the fingertips and lips.
Basal Lamina
The stratum basale (germinativum) is attached to the basal lamina (basement layer) which separates the epidermis from the dermis. The cells are attached to the basement layer via hemidesmosomes.
Types of skincare products
Serum
Serums emerged in the skincare world around the late 20th century as a response to the growing demand for targeted skincare solutions. Initially, they were used mainly in professional skincare routines but gradually became popular among consumers due to their potent, concentrated formulas.
A serum is a lightweight, fast-absorbing liquid or gel that contains a high concentration of active ingredients like vitamins, antioxidants, and peptides. Serums are designed to target specific skin concerns such as ageing, dark spots, hydration, or acne. Due to their small molecular structure, they penetrate deeper into the skin layers than other products.
Toner
Toners have been used in skincare routines for centuries, evolving from simple herbal water solutions to more complex formulations. Initially, toners were primarily astringent-based, aimed at balancing the skin’s pH after cleansing. However, over time, they have evolved to serve various purposes beyond just pH balance.
Specifically, a toner is a liquid product applied after cleansing to remove any remaining impurities, hydrate the skin, and prepare it for the next steps in the skincare routine. Additionally, modern toners can address different skin needs, such as exfoliation, soothing, and hydration. Moreover, they come in various forms, including mists, sprays, or pads, offering versatility in application methods.
Moisturiser
Moisturisers have been a fundamental part of skincare for thousands of years, with ancient civilizations like the Egyptians using oils and fats to keep their skin hydrated. The modern moisturiser, as we know it, became popular in the 20th century as cosmetic science advanced, allowing for the creation of more sophisticated, skin-friendly formulations.
A moisturiser is a cream, lotion, or gel designed to hydrate the skin, maintain its moisture barrier, and protect it from environmental damage. Moisturisers contain humectants (like glycerin), emollients (like oils), and occlusives (like petrolatum) that work together to keep the skin soft, smooth, and hydrated. They are essential for maintaining skin health, particularly in dry or harsh climates.
Oil
The use of oils in skincare dates back to ancient times, with civilizations like the Greeks, Romans, and Egyptians using olive oil, almond oil, and other natural oils for cleansing, moisturising, and protecting the skin. Over time, oils fell out of favour in Western skincare but have seen a resurgence in recent years with the rise of natural and holistic skincare approaches.
Facial oils are concentrated oils derived from plants, nuts, or seeds, used to nourish, hydrate, and protect the skin. They are rich in essential fatty acids, vitamins, and antioxidants. Oils can be used alone or layered with other products, and they are particularly beneficial for dry, mature, or dehydrated skin. They help to lock in moisture, repair the skin’s barrier, and provide a radiant glow.
Ingredients in skincare products
Hydroxy Acids in skincare products
Alpha-Hydroxy Acids (AHAs)
Alpha-hydroxy acids reduce the calcium ion concentration in the epidermis and remove calcium ions from the cell adhesions by chelation. This mechanism allows for desquamation and is further enhanced by the cleavage of the endogenous stratum corneum chymotryptic enzyme on cadherins.
Beta-Hydroxy Acids (BHAs)
Beta-hydroxy acids (salicylic acid) acts at the level of transcription to downregulate the production of fibrinogen and fibronectin necessary for bacterial replication in host tissues. BHAs are oil soluble, which means that they penetrate deeper into the epidermis.
Poly-Hydroxy Acids (pHAs)
PHAs and PHBAs act in a very similar way to AHAs, except that they have a larger structure and bigger molecular weight, which means that they are unable to penetrate even the outermost layers of the stratum corneum. This property means that they are much gentler exfoliants compared to both BHAs and AHAs, making them more suitable for people with sensitive skin.
Ceramides in skincare products
Ceramides are lipids which make up a large proportion of the lamellar sheets present in the intercellular spaces of the stratum corneum. They are synthesised from two parts: a C18-sphingoid base and a fatty acid, linked together by an amide bond.
The stratum corneum is made up of a ‘brick and mortar’ structure. Keratinocytes pushed through from the basal to the horny layer are suspended in a mixture of fatty acids, cholesterol and you guessed it: ceramides.
The stratum corneum is a barrier separating the internal environment from our surroundings. It is designed to keep the internal environment in, and the external environment out. The intercellular space between the keratinocytes in the stratum corneum plays a major role in the skin’s permeability, barrier function and effect on the skin’s structural properties. Ceramides are a major component of this intercellular space.
These molecules in the stratum corneum form structures with a low permeability which limit molecular diffusion across the lipid matrix. Ceramides are able to create this barrier due to their unique chemical structures consisting of a polar and non-polar region.
These molecules consist of a polar and non-polar region. The polar heads of the sphingoid base moieties are charged, unlike the fatty acid chains. Particles of the same charge repel each other; therefore, the ceramides orientate themselves with their polar groups facing outwards, with the non-polar region in the middle. This structure is more stable than any other configuration, and with the fatty acid moiety of ceramides having largely saturated carbon chains, they are able to pack very tightly. This leads to the formation of a continuous solid crystalline phase with a diffusion coefficient of <10-4(which to me and you means: very low).
This low coefficient of diffusion means that molecules struggle to penetrate the barrier. A healthy skin barrier will help prevent trans epidermal water loss (TEWL), from the dermis to the external environment, meaning it helps to keep the skin hydrated.
Peptides in skincare products
Peptides are biological substances which can take many different forms and perform an array of biological functions. They are made up of amino acids joined together by peptide bonds. There are 20 known amino acids, the uniqueness of which is determined by the R group (as displayed in the diagram below).
Skincare peptides can be divided into four distinguished types based on their functionalities. The four types are: signalling peptides which function as chemical messengers to the skin, carrier peptides which are able to deliver actives into the skin, enzyme inhibiting peptides which inhibit (prevent) the actions of enzymes in the skin, and finally, neurotransmitter inhibiting peptides inhibit (prevent) chemical releases at the neuromuscular junction.
Signalling Peptides
When skin is injured, proteases break down damaged tissue into different peptide fragments. These peptides act as messengers to signal skin to produce different types of tissue to promote healing. Applying peptides tricks skin into thinking that it is injured and needs to make additional types of proteins. Signalling peptides typically contain an active amino acid sequence that can induce or inhibit the formation of a specific type of protein.
Examples of signalling peptides:
- Biopeptide-CL
- Common name: Pal-GHK
- Peptamide-6
- Common name: FVAPFP
- Pal-KTTKS
- Common name: Matrixyl
- Human growth hormone
- Common name: hGH
- Transforming growth factors
- Common name: TGFα and TGFβ
Carrier Peptides
Carrier peptides act as facilitators to transport important trace elements (such as copper and manganese) necessary for wound healing and enzymatic processes. These peptides and proteins are known as penetrating peptides or membrane transduction peptides and have basic transduction domains in their structure.
The main peptide used in transporting copper is the Copper Tripeptide Complex, also known as GHK-Cu. When applied topically to the skin, the peptide functions as an antioxidant, which promotes collagen and elastin production. This mechanism allows for the reduction in fine lines and wrinkles after prolonged use.
Example of Carrier peptides:
- Copper tripeptide complex
- Common name: GHK-Cu
Enzyme-inhibiting peptides
Enzyme-inhibitor peptides act directly or indirectly to inhibit an enzyme. Due to the vast diversity of enzymes, each peptide in this category is unique and serves a distinctive function. Some inhibit the formation of proteinases (enzymes which break down proteins in the skin) and others inhibit lipid peroxidation (the degradation of lipids in the skin).
Examples of Enzyme-inhibiting peptides
- Soybean protein/amino acids
- Common name: Preregen
- Silk protein
- Common name: Sericin
- Rice peptides
- Common name: Colhinin
Neurotransmitter-inhibiting peptides
Smiling, frowning, grinning, or even maintaining a resting bitch face – your facial muscles are constantly working and moving your skin. Consequently, neurotransmitter-inhibiting peptides work to inhibit acetylcholine (a neurotransmitter) release at the neuromuscular junction, which results in a muscle paralysis-like effect. In other words, it’s like Botox in a bottle! Specifically, these peptides work by reducing muscle contractions, which, in turn, can help reduce the appearance of wrinkles. The less your facial muscles move (especially around the eyes) the less wrinkles can be formed.
Examples of Neurotransmitter-inhibiting peptides
- Acetyl hexapeptide-3
- Common name: Argireline
- Pentapeptide-18
- Common name: Leuphasyl
- Pentapeptide-3
- Common name: Vialox
- Tripeptide-3
- Common name: Syn®-Ak
Niacinamide in skincare products
Niacinamide is a hydrophilic, biologically active form of vitamin B3 commonly used in the cosmetic industry as a versatile ingredient due to its various skin benefits. Topical niacinamide has been proven non-toxic and safe for use in cosmetic products.
Niacinamide, also called Nicotinamide, is a physiologically active amide of vitamin B3. Nicotinic acid is converted into niacinamide in the body, and both have similar vitamin efficacy but different pharmacological activities. Niacinamide is a pyridinecarboxamide, meaning a pyridine with a carboxamide group. Niacinamide is an essential precursor of coenzymes, such as nicotinamide adenine dinucleotide (NAD+), nicotinamide adenine dinucleotide phosphate (NADP+), and their reduced forms (NADH and NADPH). For anyone who has studied A-level biology, you will be familiar with these molecules from the process of glycolysis (the first step in the respiratory process). These nucleotide coenzymes provide a wide range of activity, and their homeostatic balance can be corrected via the topical application of niacinamide.
In the dermatological and cosmetic field, niacinamide has been used for decades to improve skin appearance, and its efficacy has been supported by robust in vivo and in vitro studies. Niacinamide acts as an antioxidant and shows inhibition in the generation of reactive oxidative species (ROS) in human keratinocytes (cells found in the skin).
Niacinamide is described as pyridine-3-carboxamide. This means that it consists of a pride group (a chemical related to benzene with a replacement of one carbon with a nitrogen) and a carboxymide attached at the 3rd position (similar to a carboxylic acid group, but with an NH2 group instead of OH group).
There are three main theories on how niacinamide works:
Tyrosinase Inhibition
Tyrosinase is a substrate required for the synthesis of melanin. If tyrosinase is not present at the site of melanin production (melanocytes), melanin can simply not be synthesised. This simple mechanism of action suggests that the inhibition of tyrosinase will prevent the synthesis of melanin, and therefore, overtime reduce the appearance of hyperpigmentation.
Despite all studies using a different methodology to evaluate niacinamide’s tyrosinase inhibitory potential, the results are all positive and support the hypothesis that niacinamide affects enzyme TRA.
Melanin Content inhibition
In the N1 and N2 studies, the melanin content was determined by measuring the spectrophotometric absorbance of extracellular melanin content. Importantly, both studies showed a statistically significant reduction in melanin content after the NA application. Furthermore, based on these results, the NA provided a dose-dependent reduction in melanin.
Interactions in the early stages of melanogenesis
The authors tested the effects of different combinations of actives, including NA, Vitamin C and Polydeoxyribonucleotide (PDRN), on melanin content. The NA alone and in combination with other actives (Vitamin C and PDRN) showed a reduction of melanin content. Overall, as a single compound, PDRN demonstrated the highest reduction in melanin, and as a combination, PDRN, vitamin C and NA (PVN) were the most potent. Therefore, these compounds, PDRN and PVN, were further tested and compared with HQ. The below image illustrates two pathways for skin elasticity and pigmentation and features the main components investigated in study 3.
Formulation of skincare products
Chemical exfoliant
Ingredient | Maximum concentration (% w/w) |
Emollients, humectants | 40 |
Oils | 30 |
Emulsifying agents, anionic, amphoteric, non-ionic surfactants | 25 |
Ethanol (alcohol, alcohol denat.) | 25 |
Silicones including volatile silicones | 20 |
Chemical exfoliating agents | 10 |
Additional ingredients | 10 |
Thickeners | 5 |
Preservatives, antimicrobials | 1 |
Parfum | 1 |
Aqua | to 100 |
Ingredient types and functions in chemical exfoliants
Emollients, Humectants – 40%
These ingredients help in moisturising the skin by attracting water and retaining moisture, making the skin feel softer and smoother. Examples: glycerin, propylene glycol, butylene glycol.
Oils – 30%
Oils provide nourishment, lubrication, and create a protective barrier on the skin, preventing moisture loss. Examples: sunflower oil, jojoba oil, mineral oil.
Emulsifying Agents, Anionic, Amphoteric, Non-Ionic Surfactants – 25%
These agents stabilise formulations containing both oil and water by helping them to mix evenly. Examples: sorbitan stearate, TEA-stearate
Ethanol (Alcohol, Alcohol Denat.) – 25%
Ethanol is used as a solvent and penetration enhancer. It also has astringent and antimicrobial properties.
Silicones – 20%
Silicones provide a smooth, silky feel to the skin and can form a breathable barrier, protecting the skin. Examples: cyclopentasiloxane, dimethicone.
Chemical Exfoliating Agents – 10%
These acids in skincare products help in removing dead skin cells, promoting skin renewal and a brighter complexion. lactic acid, glycolic acid, salicylic acid.
Additional Ingredients – 10%
These ingredients provide additional benefits, such as nourishment, soothing, and antioxidant properties. hydrolysed proteins, plant extracts, vitamins.
Thickeners – 5%
Thickeners increase the viscosity of the formulation, providing the desired texture and consistency. Examples: carbomer..
Preservatives – 1%
These ingredients prevent the growth of microorganisms, extending the shelf life of the product. Examples: phenoxyethanol.
Parfum – 1%
Fragrances enhance the sensory experience by providing a pleasant scent to the product.
Aqua (Water) – to 100%
Water is the primary solvent used to dissolve other ingredients and form the base of the formulation. The concentration is adjusted to bring the total formulation to 100%.
Moisturiser
Ingredient | Maximum concentration (% w/w) |
Humectants | 50 |
Oils, waxes and fats | 40 |
Silicones including volatile silicones | 20 |
Ethanol (alcohol, alcohol denat.) | 20 |
Emulsifying agents, anionic / amphoteric / non-ionic surfactants | 10 |
Bulking agents | 10 |
Film forming polymers | 5 |
Additional ingredients | 5 |
Thickeners | 5 |
Preservatives, antimicrobials | 2 |
Colourants | 2 |
Parfum | 1 |
Aqua | to 100 |
Ingredient types and functions in moisturizers
Oils, Waxes, and Fats – 40%
These are essential for moisturising and providing a barrier to lock in moisture. Examples: sunflower oil, olive oil, petroleum jelly, paraffin oil, cetyl alcohol, stearyl alcohol.
Silicones – 20%
Silicones in skincare products give the formulation a smooth, silky feel and help to form a protective barrier on the skin. Examples: cyclopentasiloxane, dimethicone.
Ethanol (20%)
Ethanol, also known as alcohol or alcohol denat., is used as a solvent and can help other ingredients penetrate the skin.
Emulsifying Agents, Anionic / Amphoteric / Non-Ionic Surfactants – 10%
These help to mix oil and water components in the formulation. Examples: glyceryl stearate, sodium cocoyl isethionate.
Bulking Agents – 10%
These are used to increase the volume of the formulation. Examples: silica, talc.
Film-Forming Polymers – 5%
These ingredients form a thin, protective film on the skin. Examples: PVP (Polyvinylpyrrolidone).
Additional Ingredients (5%)
These include various beneficial additives like vitamins and plant extracts. Examples: tocopheryl acetate (vitamin E), ascorbic acid (vitamin C), aloe vera, green tea extract.
Thickeners – 5%
Thickeners are used to give the product the desired consistency. Example: carbomer.
Preservatives, Antimicrobials – 2%
These ingredients prevent the growth of bacteria and extend the shelf life of the product. Examples: phenoxyethanol, ethylhexylglycerin.
Colourants – 2%
Colourants are added to give the product a specific colour. Examples: iron oxides (CI 77491, CI 77492, CI 77499), titanium dioxide (CI 77891).
Fragrance (1%)
Fragrance is added to give the product a pleasant scent.
Water (Aqua) – to 100%
Water is the continuous phase in most moisturisers. The ratio of water to oil will dedicate the rheology of the product.
Toner
Ingredient | Maximum concentration (% w/w) |
Ethanol (alcohol, alcohol denat.) | 70 |
Humectants | 25 |
Plant extracts | 10 |
Oils Examples: vegetable, mineral | 5 |
Silicones including volatile silicones | 5 |
Emulsifying agents, anionic, amphoteric, non-ionic surfactants | 5 |
Thickeners | 2 |
Preservatives, antimicrobials | 2 |
Parfum | 1.5 |
Colourants | 1 |
Aqua | to 100 |
Ingredient types and functions in toners
Ethanol – 70%
Ethanol, commonly known as alcohol or alcohol denat., is used in high concentration as an astringent and to help other ingredients penetrate the skin. It also acts as a solvent.
Humectants – 25%
Humectants attract moisture from the environment into the skin, helping to keep it hydrated. Examples: Glycerin, PEG (polyethylene glycol).
Plant Extracts – 10%
These provide various skin benefits depending on the plant source, such as soothing, anti-inflammatory, or antioxidant effects. Examples: aloe vera extract, green tea extract, jasmine extract.
Oils – 5%
Oils are used in small amounts to provide nourishment and improve the skin’s barrier function. Examples: sunflower oil, coconut oil, castor oil, mineral oil (paraffinum liquidum).
Silicones – 5%
Silicones provide a smooth, silky feel and help create a protective layer on the skin. Examples: cyclopentasiloxane, dimethicone.
Emulsifying Agents, Anionic, Amphoteric, Non-Ionic Surfactants – 5%
These agents help blend oil and water-based ingredients together in the formulation. Examples: sorbitan stearate.
Thickeners – 2%
Thickeners give the toner its desired consistency/rheology. Examples: carbomer, xanthan gum, carrageenan.
Preservatives, Antimicrobials (2%)
These ingredients prevent the growth of bacteria, fungi, and other microorganisms, extending the shelf life of the toner. Examples: benzyl alcohol, parabens, phenoxyethanol.
Fragrance – 1.5%
Fragrance in skincare products are added to give formulations a pleasant scent.
Colourants – 1%
Colourants are used to give the toner a specific colour. Examples: iron oxides (CI 77491, CI 77492, CI 77499), titanium dioxide (CI 77891).
Water (Aqua)
Water is the primary ingredient in most toners, serving as a base and helping to hydrate the skin. In toners, the water may be a rose or witch-hazel water.
Skin oil
|
Ingredient |
Maximum concentration (% w/w) |
|
Ethanol (alcohol, alcohol denat.) |
90 |
|
Silicones |
30 |
|
Humectants |
20 |
|
Plant extracts |
10 |
|
Emulsifying agents, anionic / amphoteric / non-ionic surfactants |
10 |
|
Thickeners |
5 |
|
Parfum |
5 |
|
Additional ingredients |
5 |
|
Preservatives, antimicrobials |
1.5 |
|
Colourants |
1 |
|
Oils |
to 100 |
Ingredient types and functions in Skin oils
Ethanol – 90%
Ethanol, also known as alcohol or alcohol denat., is used as the primary solvent in this skin oil formulation. It helps to dissolve other ingredients, provides a light texture, and assists in the quick evaporation of the product on the skin.
Silicones – 30%
Silicones are added to give the formulation a smooth, silky feel and to create a protective barrier on the skin. Examples: dimethiconol, phenyl trimethicone, cyclomethicone.
Humectants – 20%
Humectants draw moisture from the environment into the skin, helping to keep it hydrated. Examples: glycerin, hyaluronic acid, aloe vera.
Plant Extracts (10%)
Plant extracts provide additional benefits such as soothing, antioxidant, or anti-inflammatory effects. Examples: rosemary extract, chamomile extract, soybean extract.
Emulsifying Agents, Anionic / Amphoteric / Non-Ionic Surfactants – 10%
These agents help to mix oil and water components in the formulation, ensuring a stable and uniform product. Examples: steareth-2, steareth-4, glyceryl stearate.
Thickeners – 5%
Thickeners adjust the consistency of skincare products, giving them a desirable texture. Example: dextrin palmitate
Fragrance – 5%
Fragrance is added to impart a pleasant scent to the skin oil, or natural scented oils are added. Example: lavender oil.
Additional Ingredients – 5%
This category includes various beneficial additives such as antioxidants, colourants, and water.
Preservatives, Antimicrobials – 1.5%
These ingredients are included to prevent the growth of bacteria, fungi, and other microorganisms, extending the product’s shelf life. Examples: benzyl alcohol, parabens, phenoxyethanol.
Colourants – 1%
Colourants are added to give the formulation its specific colour. Yellow or orange are popular so iron oxide yellow (CI 77492) is commonly used.
Oils – 100%
Oils are used to nourish and hydrate the skin, providing essential fatty acids and enhancing the skin’s barrier function. Examples: Jojoba oil, rosemary oil, rosehip oil, argan oil.
Regulation of skincare products
Active restrictions
Annex II lists the prohibited ingredients in cosmetics, these include actives which are deemed unsafe for use in cosmetics (although may be permitted in drugs or over the counter products).
Annex III lists the restricted ingredients which are permitted so long as they are below the restriction threshold(s) set out by the regulation. Many skincare actives are listed in this annex.
Retinol
The EU published Regulation (EU) 2024/996 in April 2024, amending Regulation (EC) No 1223/2009 of the European Parliament and the Council regarding the use of Vitamin A, Alpha-Arbutin, Arbutin, and certain substances with potential endocrine-disrupting properties in cosmetic products. This regulation establishes new restrictions for ‘Retinol,’ ‘Retinyl Acetate,’ and ‘Retinyl Palmitate,’ also known as Vitamin A. The amendment states, “the use of Retinol, Retinyl Acetate, and Retinyl Palmitate should be restricted to a maximum concentration of 0.05% RE in body lotion and 0.3% RE in other leave-on and rinse-off products.”
Hydroxy Acids
The Scientific Committee on Consumer Safety (SCCS) has published an updated position paper concerning consumer safety of alpha-hydroxy acids (SCCNFP/0799/04). It investigates the effects of alpha-hydroxy acids (AHAs) on the skin’s barrier function, UV exposure and the evaluation of long-term safety. The paper concluded, “Whilst the SCCNFP previously agreed that available data showed no increase in TEWL or dermal penetration of reference compounds after long-term use of AHA (up to 10% at pH 3.5), researchers raised concerns about potential effects occurring after short-term use before the skin adapts. Considering the skin renewal rate, any maximum effect on skin barrier function should be visible between 8-14 days. From the obtained results, we can deduce that AHA application does increase UV damage to the skin.”
Niacinamide
Niacinamide is generally accepted as a safe cosmetic ingredient with minimal concern over its short term and long term effects on human health. Niacin is also used in non-cosmetic products and as part of the human diet, (similar to Vitamin A).
Ceramides
The many forms of ceramides are not listed in annex II or III of the cosmetic regulation. Typically a combination of different ceramides are often used in cosmetic formulations so it can be difficult to analyse the safety of the combination of many ceramides. The ceramide group is generally ‘inactive’ and is used as a substitute for missing compounds in the skin, so it has no official restriction.
Peptides
The peptide family differs widely in their uses and chemical structures, so each individual peptide needs to be regulated individually. A good way to check the legal status and SCCS opinions of ingredients is through CosIng (Cosmetic Ingredient Database Search). Although sometimes out-of date, the CAS number can be used to check the cosmetic annexes.
Safety Assessment
Safety assessments are carried out for every cosmetic product placed on the market in the EU & UK. It is the substantiation of safety mandated by the EU cosmetic regulation (EC) No. 1223/2009. A safety assessment takes into account the following criteria:
- Quantitative and qualitative composition of the cosmetic product.
- Physical/chemical characteristics and stability of the cosmetic product.
- Microbiological quality.
- Impurities, traces, information about the packaging material.
- Normal and reasonably foreseeable use.
- Exposure to the cosmetic product.
- Exposure to the substances.
- Toxicological profile of the substances.
- Undesirable effects and serious undesirable effects.
Safety assessments are very important for skincare products especially products which contain active ingredients such as hydroxy acids which are potentially corrosive.
Claims of skincare products
Non-permitted claims
Anti-acne skincare products
Anti-acne claims are not permitted in the EU & UK because acne is a skin disorder. Cosmetic skincare products cannot treat any ailments, they can only perform cosmetic functions and potentially prevent ailments as secondary claims.
The claim “helps reduce the appearance of blemishes” is a very borderline and ‘cheeky’ claim. The word “blemish” is not very well defined in skincare products and could mean any imperfection on the skin’s surface. This ambiguity gives regulators and brands a margin of lea-way when it comes to claims. This is not an approach I would personally recommend, but you will see brands undertake this approach.
In the USA, anti-acne claims are permitted for OTC (over the counter) products, but not cosmetics. The regulatory requirements for OTC products differ from those of cosmetics, but you can make anti-acne claims.
Unsubstantiated Ingredient claims
It has been a recent trend in the industry to make ingredient claims such as “contains niacinamide to brighten your skin”. This trend has risen due to the customers’ interest in the functionality of cosmetics but has also led to a rise in unsubstantiated claims.
It is true that niacinamide can help to improve the appearance of dark spots, however, the concentration of the ingredient is critical.If you use 0.005% niacinamide in the formulation, no matter how frequently you use the product, the niacinamide won’t provide its skincare benefits. However, a product with 10% niacinamide is likely to help with dark spots. Just because a product contains an active, doesn’t mean it will actually be ‘active’ in the formulation.
Contains claims in skincare products
Budget brands often use “contains claims” to bulk out their marketing copy for a product without much expenditure or risk, whilst still making a product appeal to consumers. “Contains Niacinamide” is a claim which doesn’t promise anything and requires no more substantiation other than a formulation check to ensure it is in fact in the product. This can be seen as misleading by some customers, but contains claims have been used throughout industry and are widely accepted.
Permitted claims
Anti-ageing
Claims relating to ageing are permitted on the whole. Ageing is a natural phenomenon and not an ailment, therefore, it is in a different category from anti-acne (which is a skin disorder). Age in the cosmetics industry is a perceived factor, the perception of age can be altered. A part of the cosmetic definition is “change their appearance”, which can alter the perceived age. It’s important not to be deceiving – makeup can alter the perceived age of an individual, but does that mean it is anti-ageing, and more importantly, can it claim to be anti-ageing?
Anti-ageing claims typically focus on the long-term effects of products, but can also refer to the short term effects of hydration and plumpness of the skin.
Improves skin elasticity over 3 months
You can substantiate higher-risk claims; however, you should carefully design clinical, consumer perception, and instrumental studies to support these claims. Typically, big players in the industry, who have the time and finances, reserve these types of claims for themselves.
