In this article about moisturising products you will learn about how the skin naturally keeps itself moisturised, how water is delivered to the skin and how to prevent excessive water loss through the skin (transepidermal water loss). You will also learn about the different product types, ingredients, formulation and regulation of moisturising products in the cosmetics industry.
Skin’s Natural Moisturising System
Despite what skincare experts may tell you online, your skin naturally hydrates itself and doesn’t require hydration from the outside. In fact, it’s impossible to hydrate your skin from the outside due to the anhydrous water-repellant stratum corneum which makes up the outermost layer of the skin. All skin hydration comes from the inside out, and to best hydrate your skin, drink some water. Water from our diet is carried in our bloodstream and delivered to cells. Capillaries (the smallest type of blood vessel closest to the organs) deliver all the required oxygen, water, minerals and vitamins required for the healthy functioning of the skin, and carbon dioxide, waste reactants are carried away and excreted out of the body.
Hypodermis (Superficial Fascia)
Thickness: 1,000 μm.
Location: beneath the dermis, bottom-most layer of the ‘skin’.
Main Function: storage and supply of energy.
Superficial fascia is found directly under the skin and superficial adipose layers. It can show stratification both grossly and microscopically. Traditionally, it is described as being made up of membranous layers with loosely packed interwoven collagen and elastic fibres. This layer of the skin contains vital skin appendages, connecting the skin to the rest of the body.
Hypodermis Skin Appendages
Artery
Arteries carry oxygenated blood to organs, including the skin. Their blood carries nutrients vital for cell division. These are delivered via capillaries which reach from the hypodermis up to the papillary dermis.
Vein
Veins carry deoxygenated blood and waste produced by cells from organs, which are later re-oxygenated or disposed of.
lymphatic vessels
These vessels help regulate fluid levels in the body, receive waste products from tissues, and transport a fluid called lymph that defends the body against infection.
Reticular Dermis
Thickness: 600 μm.
Location: in between the papillary dermis and hypodermic.
Main Function: provide strength, rigidity and elasticity to the skin.
The reticular layer is the bottom layer of your dermis. It’s thick, and it contains blood vessels, glands, hair follicles, lymphatics, nerves and fat cells. A net-like structure of elastin fibres and collagen fibres surrounds the reticular dermis. These fibres support your skin’s overall structure, as well as allow it to move and stretch. This is the ‘bulk’ of the skin which houses skin appendages.
Dermis Skin Appendages
Pilosebaceous Unit
Hair follicles are present at a fractional area of about 1/1000 of the skin surface, except on the lips, palms of the hands, and soles of the feet. The sebaceous gland associated with each hair follicle secretes sebum, which is composed of free fatty acids, triglycerides, and waxes. Sebum protects and lubricates the skin, and maintains the skin surface at a pH of about 5. The arrector pili muscle attaches the follicle to the dermis and allows the hair to respond to cold and fear.
Eccrine Sweat gland
Humans have approximately 2–4 million eccrine sweat glands in total and are found on both glabrous (palms, soles) and non-glabrous (hairy) skin. Gland density is not uniform across the body surface area. The highest gland densities are on the palms and soles and respond to emotional as well as thermal stimuli.
Apocrine Sweat Gland
Apocrine sweat glands are located primarily in the axilla, breasts, face, scalp, and the perineum. These glands differ from eccrine glands in that they are larger and open into hair follicles instead of onto the skin surface. In addition, although present from birth, the secretory function of apocrine glands does not begin until puberty. Apocrine glands produce viscous, lipid-rich sweat, which also comprises proteins, sugars, and ammonia. The function of apocrine glands in many species is generally regarded as scent glands involved in production of pheromones (body odour), although this social/sexual function is rudimentary in humans.
Apoeccrine Sweat Gland
Apoeccrine glands develop from eccrine sweat glands between the ages of approximately 8 to 14 years and increase to as high as 45% of the total axillary glands by age 16–18. They are intermediate in size, but as the name suggests, apoeccrine glands share properties with both eccrine and apocrine glands. Like apoeccrine glands, apoeccrine glands are limited in distribution, as they are contained to only the axillary region. The function of this secretion is unknown, but unlikely to play a significant role in thermoregulation since evaporation is inefficient in the axilla region.
Capillaries
A large vascular network located within the dermis regulates body temperature, supplies nutrition and oxygen to tissues, eliminates toxins and waste products from tissues, and promotes immune response and wound healing. The skin has arteriovenous anastomoses in addition to tiny capillaries. They enable the fast blood flow necessary for temperature adjustment by allowing direct shunting of up to 60% of cutaneous blood flow between arteries and veins.
Types of Moisturising Products
Skin Gel
Skin gels, often water-based, emerged as a lightweight alternative to creams and lotions. They gained popularity in the late 20th century due to their fast-absorbing nature and non-greasy feel. Gels can contain hydrating agents, soothing ingredients like aloe vera, or active ingredients for specific skin concerns, such as acne treatment.
Skin gels typically contain humectants like glycerin or hyaluronic acid that draw moisture into the skin. Their water-based formulation provides hydration without adding excess oil, making them ideal for oily or acne-prone skin types.
Petroleum Jelly
Discovered in 1859 by Robert Chesebrough, petroleum jelly, commonly known as Vaseline, was initially used to treat cuts and burns. Its protective and hydrating qualities quickly made it a staple for skin care.
Petroleum jelly is an occlusive agent that forms a water-resistant barrier on the skin, preventing moisture loss. It’s highly effective in protecting dry, cracked skin and promoting healing by keeping out bacteria and environmental irritants.
Lip Oils & Balms
Lip balms have been used for centuries, with early versions made from natural oils and waxes to soothe and protect lips. On the other hand lip oils gained popularity more recently, combining the hydrating properties of oils with a glossy finish.
These products provide a protective barrier to lock in moisture. Balms often include waxes like beeswax, while oils are rich in fatty acids that nourish and soften the lips, preventing dryness and chapping.
Skin Oil
The use of oils for skin care dates back thousands of years, with ancient civilizations like the Egyptians and Romans using olive oil, almond oil, and other natural oils for moisturization and protection. In recent years, skin oils have seen a resurgence as multi-purpose beauty products.
Skin oils provide deep hydration by penetrating the outer layer of the skin, replenishing lost lipids, and restoring the skin’s natural barrier. Rich in essential fatty acids, vitamins, and antioxidants, they help lock in moisture, reduce inflammation, and improve skin texture.
Moisturiser
Moisturisers have evolved significantly since early skincare practices, which used natural emollients like animal fats and plant oils. Modern moisturisers, developed in the 20th century, are complex formulations designed to hydrate, protect, and sometimes treat the skin.
Moisturisers work by combining humectants (which draw water into the skin), emollients (which smooth and soften the skin), and occlusives (which create a barrier to lock in moisture). This combination helps maintain skin hydration, smoothness, and elasticity, making moisturisers essential for daily skin care.
Ingredients in Moisturising Products
Glycerin
Glycerin is a powerful humectant, meaning it attracts water from the environment and deeper layers of the skin to the outer layer. By drawing moisture to the skin’s surface, it helps maintain hydration and improves the skin’s barrier function. This results in smoother, softer skin and helps to keep it from becoming dry and flaky. Glycerin is commonly found in lotions, creams, and serums due to its lightweight feel and effectiveness in hydrating all skin types, including sensitive and acne-prone skin.
Hyaluronic Acid
Hyaluronic acid is renowned for its ability to hold up to 1,000 times its weight in water, making it one of the most effective hydrating ingredients. It works by binding water to the skin, boosting hydration levels, and plumping up the skin, reducing the appearance of fine lines and wrinkles. It is frequently used in serums, moisturisers, and sheet masks. Its versatility and ability to hydrate without being heavy or greasy make it a staple in both anti-aging and daily skincare products.
Petrolatum/Mineral Oil
Petrolatum and mineral oil are occlusive agents that form a barrier on the skin’s surface, sealing in moisture and preventing water loss. This barrier also protects the skin from environmental irritants and helps soothe and heal dry or damaged skin. These ingredients are key components in products like ointments, balms, and heavy-duty moisturisers, making them particularly useful for very dry or compromised skin conditions.
Natural Oils
Natural oils, such as jojoba, coconut, and argan oil, are rich in essential fatty acids, vitamins, and antioxidants. They act as emollients, replenishing the skin’s lipid barrier and providing deep hydration. They help lock in moisture, reduce inflammation, and improve skin texture and elasticity. Used in moisturisers, face oils, and body lotions, natural oils are especially popular in clean and natural beauty products for their nourishing properties and skin-soothing benefits.
Squalane
Squalane, a hydrogenated form of squalene, is a lightweight and non-comedogenic oil that mimics the skin’s natural sebum. It acts as an emollient, helping to restore the skin’s lipid barrier, locking in moisture, and providing a silky, non-greasy finish. It is particularly effective at preventing moisture loss and balancing oil production.Squalane is often used in facial oils, serums, and moisturisers, especially for those with sensitive or acne-prone skin due to its gentle and non-irritating nature.
Plant Extracts (Aloe Vera)
Aloe vera is a natural humectant and emollient that hydrates the skin by drawing moisture into the outer layer. It also has soothing and anti-inflammatory properties, making it ideal for calming irritated or sunburned skin while maintaining hydration. Found in gels, creams, and after-sun products, aloe vera is often used for its dual benefits of hydration and skin-soothing effects, making it a favourite in cosmetic formulations.
Formulation of Moisturising Products
Skin Gel
Ingredient | Maximum concentration (% w/w) |
Ethanol, isopropanol (alcohol, alcohol denat, isopropyl alcohol) | 70 |
Emollients, humectants | 20 |
Additional ingredients | 10 |
Emulsifying agents, anionic, amphoteric, non-ionic surfactants | 6 |
Thickeners | 5 |
Preservatives, antimicrobials | 3.5 |
Colourants | 1 |
Parfum | 1 |
Aqua | to 100 |
Ingredient types and functions in Skin Gels
Alcohols (Ethanol, Isopropanol) – 70%
Act as solvents and antimicrobial agents, providing quick-drying effects and preserving the formulation. Common examples include ethanol, alcohol denat, and isopropyl alcohol.
Emollients and Humectants – 20%
These ingredients help to moisturise and soften the skin by attracting and retaining moisture. Examples include propylene glycol and glycerin.
Additional Ingredients (Vitamins, Plant Extracts) – 10%
These ingredients provide specific skincare benefits such as antioxidant protection, soothing, or skin nourishment. Examples include vitamins like Vitamin E or C and plant extracts like aloe vera or chamomile.
Emulsifying Agents and Surfactants – 6%
Emulsifiers and surfactants help to mix oil and water components, improve the texture, and enhance the cleansing properties of the gel. Common surfactants include fatty acid polyglycolethers, which can be anionic, amphoteric, or non-ionic.
Thickeners – 5%
Thickeners give the gel its consistency and help stabilise the formulation. A common thickener used is carbomer.
Preservatives and Antimicrobials – 3.5%
These ingredients prevent microbial growth and extend the shelf life of the product. Examples include parabens and phenoxyethanol.
Colourants – 1%
To give the gel its desired appearance. Common colourants are often synthetic dyes or natural pigments.
Parfum (Fragrance) – 1%
Fragrance enhances the sensory experience of using the gel, providing a pleasant scent.
Aqua (Water) up to 100%
Water acts as a solvent for other ingredients and makes up the balance of the formulation to reach 100%.
Petroleum Jelly
Ingredient | Maximum concentration (% w/w) |
Petrolatum | 100 |
Parfum | 0.5 |
Ingredient types and functions in petroleum jelly
Petrolatum – up to 100%)
Petrolatum, also known as petroleum jelly, is a semi-solid mixture of hydrocarbons derived from petroleum. It is the main component in the formulation and acts as an occlusive agent, creating a barrier on the skin that helps to lock in moisture and protect against environmental factors. It is widely used for its emollient properties, providing hydration and soothing dry, irritated skin. Example: White petrolatum, USP grade.
Parfum – 0.5%)
Parfum, or fragrance, is added to the formulation to impart a pleasant scent, enhancing the user experience. Although used in minimal amounts, it can vary widely in composition, often including a blend of natural and synthetic aromatic compounds. Example: A light floral or vanilla fragrance suitable for skin and lip care products.
Lip care Products
Ingredient | Maximum concentration (% w/w) |
Oils, waxes and fats | 90 |
Humectants | 50 |
Aqua | 50 |
Film forming agents | 30 |
Silicones | 20 |
Thickeners | 15 |
UV filters | 15 |
Bulking agents | 10 |
Emulsifying agents | 5 |
Cosmetic colourants | 5 |
Ethanol (alcohol, alcohol denat.) | 5 |
Additional ingredients | 5 |
Parfum | 2 |
Preservatives, antimicrobials | 1 |
Flavouring agents | 1 |
Ingredient types and functions in lip care products
Oils, Waxes, and Fats – 90%
These are the primary components, providing structure, smoothness, and moisture to the lip care product. They create a protective barrier, helping to lock in hydration. Examples: Castor oil, beeswax, shea butter.
Humectants – 50%
Humectants attract and retain moisture in the skin, helping to keep lips hydrated and soft. Examples: Glycerin, propylene glycol.
Aqua – 50%
Water acts as a solvent, providing the base for many of the water-soluble ingredients in the formulation. It helps to hydrate and dissolve other ingredients.
Film Forming Agents – 30%
These agents create a thin, protective layer on the lips, helping to seal in moisture and prolong the product’s wear time. Examples: VP/hexadecene copolymer.
Silicones – 20%
Silicones improve the product’s texture, making it smoother and easier to apply while providing a lightweight, non-greasy feel. Examples: Dimethicone, cyclomethicone.
Thickeners – 15%
Thickeners give the product its consistency, ensuring it stays on the lips without being too runny. Examples: Carbomer, hydroxyethylcellulose.
UV Filters – 15%
These protect the lips from harmful UV radiation, preventing sun damage.
Examples: Titanium dioxide (nano), zinc oxide.
Bulking Agents – 10%
Bulking agents add volume and texture, improving the product’s feel and application. Examples: Silica, nylon powder.
Emulsifying Agents – 5%
These agents help blend water and oil-based ingredients, ensuring a stable and uniform product. Examples: Trioleyl phosphate.
Cosmetic Colourants – 5%
Colourants provide the desired tint or colour to the lip care product. Examples: Iron oxides, carmine, red 7 lake.
Ethanol – 5%
Ethanol acts as a solvent and helps with the product’s preservation by inhibiting microbial growth.
Additional Ingredients – 5%
These include vitamins and antioxidants that provide added skin benefits, such as nourishment and protection against free radicals. Examples: Vitamin E – tocopherol acetate.
Parfum – 2%
Fragrance is added for a pleasant scent, enhancing the user experience. Examples: Natural essential oils.
Preservatives, Antimicrobials – 1%
These ingredients prevent microbial growth, ensuring the product remains safe for use. Examples: Phenoxyethanol, parabens, ethylhexylglycerin.
Flavouring Agents – 1%
Flavouring agents enhance the taste of the product, making it more appealing to use. Examples: Natural fruit extracts (menthol), artificial flavourings.
Skin Oil Spray
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 oil sprays
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 the product, giving it 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 Moisturising Products
Labelling requirements
Cosmetics must be labelled in accordance with the cosmetic regulation. The legislation sets out the labelling requirements for every product to be placed on the EU market. There are seven labelling requirements outlined in the cosmetic regulation. It is also important to consider legibility, minimum font sizes, claims, logos and barcodes when labelling cosmetic products.
Labelling requirements for products sold in the European Union:
- Name & address of responsible person & country of origin.
- Nominal content given by weight or volume.
- Durability – typically expressed as period after opening (PAO).
- Precautions.
- Instructions for use, unless application is understood through the product function.
- Batch number or reference for identification.
- Function of cosmetics, unless the function is clear from presentation.
- A list of ingredients following the international nomenclature of cosmetic ingredients (INCI) system.
The international nomenclature of cosmetic ingredient (INCI) names can be found in the Commision implementing decision (EU) 2022/67 of 31 March 2022 laying down rules of the application of Regulation (EC) No 1223/2009 of the European Parliament and of the Council as regards to the glossary of common ingredient names for use in labelling of cosmetic products. INCI names can also be found through an online search portal COSING – Cosmetic Ingredients.
As with every rule, there are exceptions. Some smaller or niche products are exempt from some aspects of product labelling, we will cover these in a future article which goes more in-depth into the labelling of consumer goods.
Claims of Regulation Products
TEWL-meter
Transepidermal water loss (TEWL) is a key indicator of the skin barrier function. Accurate measurements of TEWL are important for a wide range of clinical and personal care applications.
The open chamber method of TEWL measurement is based on the diffusion principle in an open chamber.
A = surface (m2), m = water transported (g), t = time (h), D = diffusion constant [=0.0877 g/m/h(mm Hg], p = vapour pressure of atmosphere (mm Hg), x = distance from skin to point of measurement (m).
The probe consists of a hollow cylinder with two pairs of sensors measuring temperature and humidity, one pair slightly higher than the other. It measures the moisture at two different sites and from this the TEWL can be calculated.
dm/dt = – D * A * dp/dx
Cutometer
The Cutometer® has a suction based measurement method. Negative pressure is created by the pump in the device. The negative pressure draws the skin into the aperture of the probe. Inside the probe is a non contact optical measuring system, consisting of a light source projected across the aperture to a light receiver, measuring the distance into the aperture that the skin travels. The resistance of the skin to being sucked into the aperture is determined by the firmness of the skin while the ability of the skin to return to its previous position is the elasticity. The results are displayed in a curve from which a series of interesting parameters can be calculated. The parameters calculated include the R-parameters, the F-parameters and the new Q-parameters.
Readings from a cutometer:
- R0: This parameter represents the passive behaviour of the skin to force.
- R1: The ability of the skin to return to its original state.
- R2: Gross elasticity, the closer to 1 (100%) the more elastic.
- R3: Maximum amplitude of last and first curves compared to give “tiring effects” of skin.
- R4: Minimum amplitude of last and first curves compared to give “tiring effects” of skin.
- R5: Net elasticity, the closer to 1 (100%) the more elastic the skin.
- R6: Portion of visco-elasticity on the elastic part of the curve (the smaller the value the higher the elasticity).
- R7: Portion of elasticity compared to complete curve, closer to 1 (100%) the more elastic.
- R8: Ability of the skin to return to normal state.
- R9: Tiring effects of the skin after repeated sucking, the smaller R9 the smaller the effect.
- F1: Elasticity, the closer to 0 the more elastic (based on area of curve).
- F2: Area above the upper envelope curve.
- F3: Area within the envelope curve.
- F4: Firmness, the smaller F4 the greater the ability to resist suction.
- Q0: Maximum recovery area, decreases with increasing firmness of the skin.
- Q1: Elastic recovery, higher with greater firmness.
- Q2: Viscous recovery.
- Q3: Viscoelastic recovery (overall elasticity), higher with more skin firmness.
