The stratum corneum (SC), the outermost layer of the epidermis, functions as a protective barrier that maintains skin hydration by preventing water loss and protecting the body from foreign insult.1 Damage to the SC and disruption of skin barrier function can result in dryness, irritation, itch and induction of inflammatory cascades.2 Breakdown in the integrity of the SC can be caused by endogenous factors including a genetic predisposition and exogenous factors including poorly formulated skincare products.1,2 A proper skincare regimen of regular cleansing and moisturizing can help mitigate factors that damage the SC and help to maintain or restore the SC and skin barrier function.3
This article provides a brief overview of important cleanser and moisturizer properties in order to better prepare healthcare providers for recommending skincare products to patients.
The Basic Skincare Regimen: Cleansing and Moisturizing
The foundation of a good skincare regimen begins with regular cleansing and moisturizing. Proper cleansing removes surface dirt, oil, makeup and micoorganisms; moisturizing can replenish moisture to the skin and restore skin barrier function.3,4
The ideal cleanser is gentle, maintains skin at a pH of 5.5, minimizes skin barrier disruption and helps maintain skin moisture.3 Surfactants, often referred to as the workhorses of cleansers, are the main ingredients in cleansers and are responsible for their cleansing activity.5 Liquid cleansers are generally preferred over soaps.3 Liquid cleansers are typically acidic to maintain skin pH and utilize multiple ingredients that are specifically designed to minimize skin barrier disruption and moisturize the skin. Soaps, on the other hand, are typically formulated with alkaline surfactants, which can cause tightness, dryness and irritation.6
The ideal moisturizer is effective at hydrating the SC, reducing water loss, restoring the skin barrier and providing immediate hydration.7 The primary components of moisturizers are humectants, emollients and occlusives. Humectants help retain water by drawing water from the dermis into the epidermis and absorbing water from the environment. Emollients are oils and lipids that soften skin by increasing SC hydration.7 Emollients contribute to the smoothness often felt after application of a moisturizer. Occlusive agents create a hydrophobic barrier on the skin that reduces transepidermal water loss.
Common moisturizer ingredients are as follows:
· Humectants: glycerin, panthenol, propylene glycol, sodium and ammonium lactate, sodium pyrrolidine carboxylic acid
· Emollients: dimethicone, isopropyl palmitate, castor oil, keratin, cyclomethicone
· Occlusives: cetyl alcohol, lanolin, petrolatum, mineral oil, propylene glycol
The Science of Skincare
Unlike prescription drugs, the FDA does not require that promotional material and labeling for cosmetics and OTC drugs be submitted for FDA review.8 Therefore, some manufacturers label or promote their products with unsubstantiated or even false claims, which may prompt action by the FDA. Of particular note are products that claim to be hypoallergenic. There are no federal standards or definitions that govern the use of the term hypoallergenic in the United States.9 Therefore, claims of hypoallergenicity – and other claims in general – should be evaluated with supporting scientific evidence.
Clinical studies are often conducted by manufacturers to investigate skincare products.10 Objective measurements include clinical assessment by a trained professional as well as using instrumental methods.11 Skin hydration is evaluated by a technique known as corneometry, which measure capacitance as a proxy marker for skin hydration.12 Increases in corneometry values indicate an increase in skin hydration. Skin barrier function is assessed by measuring transepidermal water loss. High levels of transepidermal water loss indicate water loss from the skin, which corresponds to poor skin barrier function. Products that reduce transepidermal water loss are believed to help repair skin barrier function by preventing water loss from the skin. Confocal microscopy of the skin using Raman spectroscopy is an in vivo measurement that can determine the exact chemical composition of the skin.13 This technique can assess whether a moisturizer’s components are penetrating and absorbing into the skin and at what levels.
A number of skin diseases are associated with disrupted barrier function. Altered barrier function may be intrinsic to the pathophysiology of the disease, or it may be caused by unwanted side effects of topical medications.10 Because of this, these patients often have special cleanser and moisturizer needs.
Atopic dermatitis (AD) is characterized by marked skin dryness with an increase in transepidermal water loss.14 Patients with AD also have reduced SC levels of ceramides and natural moisturizing factor (NMF).15 Patients with AD should use nonsoap-based cleansers with synthetic detergents that have an acidic to neutral pH; this will reduce the potential for irritancy.16 Newer formulations of moisturizers specifically designed for patients with AD incorporate molecular components missing from the SC into their formulation as ingredients.17 These newer products rely on physiologic lipid and NMF components to restore barrier function.
Many common acne therapies can cause cutaneous drying and irritation.10 Cleansing and moisturizing can help alleviate dryness and irritation that may be associated with acne treatments. Cleansers for acne patients should be soap-free, have an acidic pH, and be alcohol-free. Moisturizers for acne patients should be low in viscosity, noncomedogenic and provide UV protection.
Rosacea patients have sensitive skin, therefore skincare products can exacerbate their rosacea and induce flares.18 Care must be taken to ensure that rosacea patients select an appropriate cleanser and moisturizer. Soap-free cleansers with an acidic to neutral pH should be chosen. Moisturizers should be noncomedogenic and contain emollients. It is also recommended that rosacea patients us a sunscreen with titanium dioxide or zinc oxide (inorganic UV filters) when outdoors.
The Foundation of Skincare
Cleansing and moisturizing should be the foundation for all skincare regimens. Proper cleansing and moisturizing can maintain and restore the SC and skin barrier function. Understanding the basics of cleansers and moisturizers can prepare healthcare providers to make recommendations to their patients. Furthermore, a good skincare regimen can help support the treatment plan for diseased skin.
Kristine Kucera is the senior physician assistant at Dermatology Center of Frisco in Frisco, Texas, and an adjunct clinical professor at the University of Texas Southwestern Medical Center and University of North Texas Health Science Center. Staci Brandt is a clinical science specialist for Galderma Laboratories, LP The authors received writing assistance from Matthew H. Meckfessel, PhD, of Galderma Laboratories, LP. The authors have completed disclosure statements and Kucera reports that she is an advisor to Novartis and Aqua and a speaker and advisor for Abbvie, Amgen, Janssen, Valeant, Bayer and Actavis.
8. FDA Authority Over Cosmetics. http://www.fda.gov/cosmetics/guidanceregulation/lawsregulations/ucm074162.htm
9. Hypoallergenic Cosmetics. http://www.fda.gov/cosmetics/labeling/claims/ucm2005203.htm
12. Heinrich U, et al. Multicentre comparison of skin hydration in terms of physical-, physiological- and product-dependent parameters by the capacitive method (Corneometer CM 825). Int J Cosmet Sci. 2003;25(1-2):45-53.
13. Cash K, High W, de Sterke J. An evaluation of barrier repair foam on the molecular concentration profiles of intrinsic skin constituents utilizing confocal Raman spectroscopy. J Clin Aesthet Dermatol. 2012;5(8):14-17.