Moisturizing agents: How to select the right grade for cosmetics?

Human skin is covered with the stratum corneum, which is a thin biological protective membrane. This stratum corneum exposed to the external world allows us to live in the dry atmosphere without losing water.

 

• The stratum corneum is thin and supple.
• It contributes to the maintenance of healthy skin by preventing loss of body water.

Healthy skin is generally said to have a water content of 10 to 20%. 

The term 'Moisturizer' resonates with the consumer and denotes improvement of skin, thus projecting the perception of healthy skin. In general terms, 'moisturization' (or skin conditioning) is the kingpin of topical skin treatment.

Skin discomfort is not acceptable, and moisturizers containing primarily emollients and humectants can help alleviate the symptoms of 'dry' skin and uncomfortable skin symptoms.
 

So, choosing the right moisturizer, skin hydrating agent, and skin softening/soothing ingredients requires:

 

• Knowledge of their chemical, physical and performance properties, as well as
• How to best utilize them against the target performance claim, consumer perception and expectations

Let's explore the classification and performance matrix of moisturizing agents.


 

Since dry skin and combinations of it require barrier repair of some type, it will be necessary to consider the incorporation of four classes of functional ingredients to achieve optimal consumer perceived moisturization.

The four classes of functional ingredients are:

 

• Humectants help to modulate water content by enhancing surface water availability.
• Occlusivity agents, typically denoted as moisturizers, modulate water content by slowing down TEWL.
• Keratolytic agents stimulate cell renewal by cleaning dead cells from the skin's surface and exciting new cells to form at the surface for a better and healthier barrier.
• Emollients provide topical aesthetics and lubrication that enhance the perception of soft, smooth skin; they can provide some level of moderate TEWL improvement topically.

 
"Moisturizer" technologies utilized to provide consumer perceived moisturization are as diverse, in a general sense, as the total available chemistry in personal care. Achieving acceptable moisturization does not necessarily require new technology, but can draw from the extensive list of already available chemistries mainly:

 

• Esters
• Hydroxyl-functional
• Vegetable oils/butters
• Organic salts, and
• Nitrogen-containing

There are many options to enhance moisturization performance in skin and hair care formulations.

Generally, there is required a balance of the four categories listed above to elicit both a consumer perceived moisturization affect and a clinical enhanced performance. Further, there is a synergistic gain when combinations of each technology classification are employed. Let's discuss each of them in detail...

 

Humectants

Group of hydroscopic substances – Attracts and retains the moisture in the air or skin.

Strengths: Ability to modulate available moisture on and in the skin.

Hurdles: Tend to be aesthetics.

Opportunities: Synergies to enhance humectancy (seen as TEWL and Conductance improvements) at reduced levels, and thus improved aesthetics and performance.

 

Occlusivity Agents

Air and Water barrier – Prevents significant evaporation of skin's internal water, and prevents topical ingredients from penetrating the skin's barrier. 

Strengths: They are natural skin's moisturization balance. 

Hurdles: Tend to be aesthetics. 

Opportunities: Utilization of petrolatum with aesthetic enhancing occlusivity agents. 

 

Keratolytic Agents

Benefits: Removal of dead skin to enhance skin barrier repair and renewal. 

Strengths: They are more rapid cell turnover to strengthen the skin's barrier. 

Hurdles: They are primarily increased skin irritation. 

Opportunities: Compatible to skin's pH mantle without loss of the keratolytic properties. 

 

Emollients

Generally noted for their enhanced skin aesthetics with improvements in tactile soft/smoothness properties. They also act as a non-greasy fiction reducer. 

Strengths: Ability to modify the skin's tactile surface perception.

Hurdles: Ability to choose the right emollients from the expansive candidates represented by a diverse selection of chemistries.

Opportunities: Understanding the emolliency cascading affects of blended emollients to trigger changing feels during and after application.

 

Vegetable and natural oils (such as rapeseed oil, sunflower oil and soybean oil, etc.) are desirable emollients offering antioxidant properties in skin care applications. Some of the oils and their properties are listed below.

 

• Wheat Germ Oil is an antioxidant with more Vitamin E than any other natural oil. It is primarily used as an emollient to moisturize and relieve dry, irritated skin. Wheat Germ Oil possesses cell regenerative properties that make it a good choice for anti-aging formulas.
• Avocado oil is deeply hydrating and highly compatible with your skin's own oils. It is also a powerful anti-oxidant and is brimming with high levels of chlorophyll, vitamin E and omegas 3 and 9 to improve the health and vitality of your skin.
• Jojoba oil has excellent inherent emollient and moisturizing properties - coupled to its oxidative stability properties. It is one of the world's top lipid cosmetic ingredients often used in anti-aging skincare.
• Cocoa Butter is one of the most stable fats known, loaded with natural antioxidants that prevent rancidity and give it a shelf life of two to five years. It softens and lubricates the skin, assisting in reducing stretch marks and scars making it an excellent massage cream. It performs as an antioxidant, emollient, and lubricant.
• Sweet almond oil has a long historical use that includes restoring itchy, dry and inflamed skin as well as being a simple emollient. It contains 24% linoleic acid, an incredibly high amount of the antioxidant EFA.
• Shea Butter is used as an emollient and moisturizer in cosmetics. High in vitamin E, an anti-aging antioxidant that increases micro-circulation, it also contains the antioxidants beta-carotene and vitamin A.

Moisturization performance is a critical balance between the consumer perception of the change in the skin characteristics and clinical validation of the claims that the product is working in a way to match up with the consumer expectations of the change in the skin's health.

 

Main Performance Expected from Moisturizers
	Source: Prohealthcareproducts.com
TEWL	Conductance
Observed Dryness	Desquamatry

The table below sums up the main performances expected from moisturizers in cosmetic & personal care applications:

 

Face Care Moisturizing Lotion

Clinique's Dramatically Different Moisturizing Lotion+

The moisture "drink" developed by Clinique's dermatologists to maintain optimal moisture balance for very dry skins, or skins dry in the cheeks, comfortable to oily in the T-zone. It softens, smooth's & improves the skin.

The big plus with a new complex is that this formula strengthens skin's own moisture barrier by 54%. More moisture stays in and the skin feels soft, springy.

 

• Combination of glycerin and urea act as a synergistic humectant, lanolin alcohol has good moisture retaining properties.
• Combination of Petrolatum, Mineral oil, and Lanolin alcohol provide good balanced moisture loss control.
• Combination of Propylene Glycol Dicaprate, Sesame oil, and Sunflower Seedcake, along with the balanced combination of butylene glycol and pentylene glycol (both also acting to enhance preservation of the system), should develop a soft smooth pliable skin surface.
• Sodium Hyaluronate, along with the glycerin will provide exfoliating keratolytic activity.

Face Care Wrinkles Repair

Rapid Wrinkle Repair® Night Moisturizer

Featuring its unique combination of Retinol SA, Glucose Complex, and Hyaluronic Acid; Rapid Wrinkle Repair® Night Moisturizer moisturizes & renews the look of skin throughout the day.

 

• It helps to smooth wrinkles fast and diminish the look of age spots.
• Skin is left feeling smooth and looking younger.

Accelerated Retinol SA fades the look of stubborn wrinkles, brightens skin tone, smooth fine lines & texture.

 

Body Care Moisturizing Lotion

Aveeno® Skin Relief 24 hr Moisturizing Lotion

This rich formula powered with ACTIVE NATURALS® Triple Oat Complex moisturizes skin for 24 hours.

 

• It is clinically shown to help relieve itchy, extra-dry skin.
• This fast-absorbing, hydrating lotion starts to work immediately to nourish and restore essential moisture to extra-dry or sensitive skin so it looks and feels healthier".

• Glycerin acts as the primary humectant.
• Combination of dimethicone, petrolatum, Shea Butter should act as acceptable occlusivity agents.
• Combination of Isopropyl Palmitate, cetyl alcohol, and Oat Kernel oil should develop a smooth skin surface.

The use of various functional agents to improve moisturization of the skin can be translated to many body parts (body, legs, hands, face, feet). So, choosing the right ingredient (humectants, emollients, occlusive agents, etc. ) for your formulation should be based on consumer perception and expectations. Explore some of the real world examples by keeping the customer's need in mind.

Simply put, different types of moisturizing agents (humectants, emollient, occlusivity agent, etc.) have entirely different concepts. They are majorly used in skin care and decorative cosmetics products because these properties are very much desirable in these formulations. Overall, for any moisturizing product, the key is more what claim and consumer experience is required, not whether one needs a humectant, occlusivity agent, emollient, etc. For instance:

 

1. If the face needs to remove the dryness of the skin, then a combination of humectants and keratolytic action would better achieve this. Through a 7-day mini regression study, the change can be followed and various formulations can be compared.
2. If the legs need to remove the scaly white flakes that can be associated with dry skin, then a combination of keratolytic agents and humectancy are the primary agents to use. Including emollient will improve the initial skin feel that denotes skin softness/smoothness.
3. If the hands have rough skin that feels tight, especially during the dry cold winter months, then a balanced combination of humectants, occlusivity agents and emollients will improve the skin's barrier to reduce the trans-epidermal water loss, while providing a soft smooth skin feel through the plasticization of stratum corneum.

Moisturizing agents are used to combat dry skin, a common problem for skins of all ethnicities. Dry skin can be caused by a number of factors - from health reasons, to contamination or contact with other materials, to environmental conditions. The lack of water in the outer layer of skin (stratum corneum) causes the skin to lose its flexibility and elasticity and becomes scaly and can crack, or even bleed. The proper amount of water and sebum in the stratum corneum can prevent these things from happening. The sebum binds with the moisture in the skin and slows down the evaporation of this moisture. This action is known as trans-epidermal water loss.

Creams, lotions, liquid makeups and foundations usually contain humectants and have good moisturizing properties. Thus, add moisture or assist in the retention of water in the skin.

In color cosmetics, using waxes or oils in a product creates lipid barriers that keep moisture in the skin. Lipsticks and lip glosses are excellent moisturizers because they produce occlusive films when applied to the lips. 

Other products that form occlusive films are bath oils, suntan oils, and ointments. Chapstick is an excellent moisturizer as it creates a very good occlusive waxy film.