INTRODUCTION
Oats (Avena sativa) have been cultivated since the Bronze Age, and the use of oats as a topical therapy for variety of dermatological conditions dates to Roman times. Initially, colloid baths were prepared by boiling oatmeal to extract the gelatinous colloidal material.1 In the early to mid twentieth century in the recorded scientific literature the term of colloidal oatmeal was beginning to appear.2 In 1945, a ready-to-use colloidal oatmeal became available, and soon after several clinical studies demonstrated its benefits as a remedy for inflamed, dry and itchy skin dermatoses.3-5 In 2003, the FDA approved the use of colloidal oatmeal as a skin protectant, and currently colloidal oatmeal is commonly used for skin rashes, erythema, burns, itch, and eczema.5,6
Despite a rich history of traditional use, the exact mechanisms of action that give colloidal oatmeal its clinical benefits remain unknown. A recent study has reported that colloidal oatmeal can reduce the expression of pro-inflammatory mediators in keratinocytes and decrease activation of the NF-κB pathway, which could contribute to the anti-inflammatory activity of colloidal oats on irritated skin.7 In addition, Chon and colleagues recently reported that a lipophilic extract isolated from oats can induce ceramide synthesis in keratinocytes through activation of the PPAR pathway.8 We conducted a series of in vitro experiments and a clinical study to help identify the mechanism of action for the clinical benefit of colloidal oatmeal on skin barrier. Extracts of colloidal oatmeal were prepared using organic and aqueous solvents to concentrate constituents based on compound
polarity, and were subjected to molecular and functional assays related to skin barrier. In addition, an investigator-blinded clinical study was conducted to evaluate the efficacy of a colloidal oatmeal skin protectant lotion in improving barrier function in moderate to severely dry skin. Results of these studies demonstrate that colloidal oats can increase skin’s expression of epidermal differentiation targets and lipids involved in barrier function, can provide pH-buffering capacity for skin and can clinically improve skin barrier function. Thus, colloidal oatmeal as an ingredient provides a multi-therapy approach for dry and compromised skin by strengthening skin barrier.
MATERIALS AND METHODS
Preparation of Extracts of Colloidal Oatmeal
Four extracts of colloidal oatmeal were prepared using HPLC-grade hexanes, 80% aqueous acetone, 80% aqueous methanol, and water to generate extracts enriched in phytochemicals based on polarity as previously described.7 For cell culture experiments, stock solutions of each extract were dissolved in DMSO (50 mg/mL) and diluted into media (DMSO < 0.01%).
In Vitro Skin Models and Treatment
Epidermal equivalents (EPI 200 HCF) were purchased from MatTek (Ashland, MA). Equivalents were topically treated (2mg/cm2) with colloidal oatmeal skin protectant lotion twice every 24 hours. Equivalents were incubated for 48 hours at 37°C with maintenance medium then tissues were harvested for the protein or mRNA expression analysis. Primary human
