K. P. Ananthapadmanabhan

Cleansing without compromise: the impact of cleansers on the skin barrier and the technology of mild cleansing

ABSTRACT:  Cleanser technology has come a long way from merely cleansing to providing mildness and moisturizing benefits as well. It is known that harsh surfactants in cleansers can cause damage to skin proteins and lipids, leading to after‐wash tightness, dryness, barrier damage, irritation, and even itch. In order for cleansers to provide skin‐care benefits, they first must minimize surfactant damage to skin proteins and lipids. Secondly, they must deposit and deliver beneficial agents such as occlusives, skin lipids, and humectants under wash conditions to improve skin hydration, as well as mechanical and visual properties. While all surfactants tend to interact to some degree with lipids, their interaction with proteins can vary significantly, depending upon the nature of their functional head group. In vitro, ex vivo, and in vivo studies have shown that surfactants that cause significant skin irritation interact strongly with skin proteins. Based on this understanding, several surfactants and surfactant mixtures have been identified as “less irritating” mild surfactants because of their diminished interactions with skin proteins. Surfactants that interact minimally with both skin lipids and proteins are especially mild. Another factor that can aggravate surfactant‐induced dryness and irritation is the pH of the cleanser. The present authors’ recent studies demonstrate that high pH (pH 10) solutions, even in the absence of surfactants, can increase stratum corneum (SC) swelling and alter lipid rigidity, thereby suggesting that cleansers with neutral or acidic pH, close to SC‐normal pH 5.5, may be potentially less damaging to the skin. Mildness enhancers and moisturizing agents such as lipids, occlusives, and humectants minimize damaging interactions between surfactants, and skin proteins and lipids, and thereby, reduce skin damage. In addition, these agents play an ameliorative role, replenishing the skin lipids lost during the wash period. The present review discusses the benefits of such agents and their respective roles in improving the overall health of the skin barrier.

Three-dimensional chemical imaging of skin using stimulated Raman scattering microscopy

Abstract. Stimulated Raman scattering (SRS) microscopy is used to generate structural and chemical three-dimensional images of native skin. We employed SRS microscopy to investigate the microanatomical features of skin and penetration of topically applied materials. Image depth stacks are collected at distinct wavelengths corresponding to vibrational modes of proteins, lipids, and water in the skin. We observed that corneocytes in stratum corneum are grouped together in clusters, 100 to 250 μm in diameter, separated by 10- to 25-μm-wide microanatomical skin-folds called canyons. These canyons occasionally extend down to depths comparable to that of the dermal–epidermal junction below the flat surface regions in porcine and human skin. SRS imaging shows the distribution of chemical species within cell clusters and canyons. Water is predominately located within the cell clusters, and its concentration rapidly increases at the transition from stratum corneum to viable epidermis. Canyons do not contain detectable levels of water and are rich in lipid material. Oleic acid-d34 applied to the skin surface lines the canyons down to a depth of 50 μm below the surface of the skin. This observation could have implications on the evaluation of penetration profiles of bioactive materials measured using traditional methods, such as tape-stripping.

A comparison between interactions of triglyceride oil and mineral oil with proteins and their ability to reduce cleanser surfactant-induced irritation

Skin irritation in personal cleansing has been correlated with surfactant binding with stratum corneum proteins. Polar and non‐polar oils are increasingly being used in cleansing formulations which contain high (10–15%) level of anionic and non‐ionic surfactants. However, the effects of oils in modulating skin damage from a cleansing product have not been studied in any detail. The objectives of this study are to determine whether low‐viscosity polar and non‐polar oils differ in their ability to reduce surfactant‐induced skin irritation and, if so, how it might be related to their interactions with proteins.

Effect of detergents on the physicochemical properties of skin stratum corneum: a two‐photon excitation fluorescence microscopy study

Understanding the structural and dynamical features of skin is critical for advancing innovation in personal care and drug discovery. Synthetic detergent mixtures used in commercially available body wash products are thought to be less aggressive towards the skin barrier when compared to conventional detergents. The aim of this work is to comparatively characterize the effect of a mild synthetic cleanser mixture (SCM) and sodium dodecyl sulphate (SDS) on the hydration state of the intercellular lipid matrix and on proton activity of excised skin stratum corneum (SC).

C.1 – Personal Cleansing

This chapter reviews mild and moisturizing cleansers. Specifically, it focuses is on how cleansers affect skin moisturization, how critical it is to prevent/minimize cleanser-induced damage as a first step towards achieving moisturization from cleansers, and finally, how to deliver moisturization benefit from cleansers. The mild-cleanser segment has grown over the years with increasing interest in achieving skin functional benefits, especially moisturization, from wash-off systems. Availability of novel chemicals such as milder surfactants and polymers coupled with an understanding of cleanser-induced changes in skin have led to novel approaches to deliver skin care benefits from cleansers. Introduction of new product forms, such as liquid cleansers, have made it easier to deliver skin care benefits from wash-off systems. Current cleanser technologies have advanced from providing simple cleansing and hygienic benefits to delivering healthy skin relevant moisturization and care benefits. These technologies have two components, the first, a relatively mild-cleanser surfactant base and the second, a moisturization package that helps to mitigate some of the surfactant damage and provide positive skin benefits. Moisturizing cleanser technologies that deposit occlusives, lipids, and oils provide measurable improvements in skin dryness and hydration.