P12. A comparison of low (ph 5.5) and neutral ph cleansers on skin Title dryness: of poster considerations for baby skin cleansing

Transcription

1 P12 Poster reference number A comparison of low (ph 5.5) and neutral ph cleansers on skin Title dryness: of poster considerations for baby skin cleansing Authors names and affiliations Visual Dryness Stacy Hawkins, Heather McGuiness, Kathleen Combs, Greg Nole, Duygu Celebi and KP Ananth Unilever R&D, Trumbull, CT, USA This work was sponsored by Unilever R&D

2 Introduction and Objectives Due to the developing nature of the newborn stratum corneum (SC) throughout the first year of life, mild cleansing is fundamental to its care. It is well known that cleansing ph can influence product mildness. Marketed baby cleansers are made within a wide range of phs. Baby cleanser phs will typically range anywhere from a ph 4 to a ph 1. The damaging effects of high ph soaps (around ph 1) on SC lipids and proteins are well established, in comparison to neutral ph synthetic detergents. Many cleansers targeted toward the pediatric population are formulated at an acidic ph, and, as such, purport enhanced compatibility with infant skin. However, it is unclear whether a cleanser formulated to match the physiological ph of healthy skin (at ph ) is, de facto, milder. The objective of this research was to measure the impact of ph and surfactants on cleanser mildness using the FCAT design, in an adult population. The forearm controlled application test (FCAT) protocol is a well-established, industry-standard exaggerated wash design for assessing product mildness. Market leading baby bar is a ph 1 soap bar that is harsh compared to a commercial neutral ph syndet bar

3 Materials and Methods Healthy subjects (approximately n~5 per study), ages years old, provided informed consent to participate in IRBapproved, double blind, randomized FCAT studies conducted in Winnipeg, Canada under dry winter conditions, with four controlled washes per day. Bars were tested for a period of 12 days whereas the liquids were tested for 5 days. Clinical evaluations included visual assessments of dryness as well as instrumental measurement of transepidermal water loss (TEWL) on the last day. Test products: Trial 1: A market leading baby cleansing soap bar (ph~1) vs a neutral ph syndet bar Trial 2: Two commercially available syndet bars at ph 5.5 were compared directly to a third marketed neutral ph syndet bar Trial 3: Non-commercial bars with same isethionate based surfactant composition were made at different phs (5.5 and 7.) so that the impact of ph alone could be studied Trial 4: Comparison of non-commercial liquid body washes formulated with identical syndet surfactant compositions differing only in their ph

4 TEWL. Day 5 or Visual Dryness, AUC PM Neutral ph Syndet Bars Are Milder Than High ph Soap Bars Mkt leading Baby Bar at high ph is harsher than neutral ph Syndet Bar TEWL day 5 FCAT Mkt Leading Baby Soap Bar, ph 1 Syndet Bar ph ~7 Visual Dryness PM

5 Change from Baseline Commercial Syndet Bars At Low ph (5.5) Generate Greater Dryness Than Those at Neutral ph Commercial Syndet Bars vs a Neutral ph Bar Visual Dryness Study Day Bar1 ph 5.5 Bar2 ph 5.5 Bar3 ph 7. Untreated

6 Change from Baseline Syndet Bars With Same Surfactant Still Generate Greater Drying at Low ph Compared to Neural ph Identical Test Bars Buffered to Different ph - Visual Dryness What drives difference between commercial bars? surfactant type or ph.8.6 Two test bars were made using same surfactant but two different phs Neutral ph bar is milder than low ph bar with same surfactant Study Day Bar at ph 5.5 Bar at ph 7. Untreated

7 Visual Dryness, CFB, AUC Syndet Body Wash With Same Surfactant is Also More Drying at Low ph Than at Neutral ph Visual Dryness Body Wash, ph 4.7 Body Wash, ph 6.7 Change From Baseline (CFB); Area Under the Curve (AUC); p<.5

8 Mg SLI Bound/mg HSC Low ph May Result in Greater Skin Damage than Neutral ph Because Anionic Surfactants Bind More Strongly to Proteins at Lower ph At low ph proteins are more positively charged resulting in increased surfactant binding Normal Skin ph High Binding ph ph Sodium Lauroyl Isethionate (SLI) Human Stratum Corneum (HSC) 6 min 1 min Low Binding ph 7-9 High Binding ph 7-11

9 Summary and Conclusions Typical surfactants used in marketed cleansers are mildest at neutral ph A neutral ph syndet bar was found to be milder than a market leading baby soap bar at ph 1 Neutral ph bars and liquid body wash formulations were found to be milder compared to formulations at low phs which were close to skin s physiological ph Increased dryness at low ph may be due to the interaction of anionic surfactants with the corneum under weak acidic conditions. Thus, the drying potential of a bar or a liquid depends upon the nature of surfactants used in making the bar and its interaction with the stratum corneum under the ph conditions of normal use Although ph 5.5 may intuitively seem to be good for skin there is no guarantee that skin-friendly ph makes a cleanser mild toward skin, as mildness depends upon how surfactants interact with skin under acidic ph conditions. These effects are likely to be even more important for infant skin because of their increased vulnerability.