Topical No. 9 Daily Liquid Exfoliant: One-Week Histologic Observations in Human Skin Explants

Wendy Ouriel, M.S. • OUMERE Labs • Updated Oct 12, 2025

Abstract

Background: Daily, gentle acidic exfoliation is central to OUMERE’s barrier-first approach. We performed an exploratory, one-week skin explant experiment comparing topical No. 9 Daily Liquid Exfoliant to a deionized water control.

Objective: To visually assess histologic differences after one week of treatment using toluidine blue staining.

Methods: Human skin explants maintained in culture were topically exposed once daily (7 days) to either No. 9 (experimental) or DI H₂O (control). Following treatment, samples were embedded, sectioned (~1000 µm), stained with toluidine blue, and examined by light microscopy. Full materials and protocol are detailed in Part 1 (link).

Results: The No. 9–treated explant displayed a visually more complex architecture with denser toluidine blue–positive fibers and conspicuous nuclei relative to control, consistent with a collagen-rich appearance.

Conclusions: Within one week, qualitative histology suggested preserved or increased collagen-associated signal and cellular complexity in the No. 9 sample versus control. Larger, quantitative studies are warranted.

Introduction

Controlled acidic turnover can normalize keratinization and support barrier integrity when formulated to be non-sensitizing and used appropriately. OUMERE No. 9 (PHA/AHA/BHA; fragrance-free) is designed for daily, gentle exfoliation as part of a minimal routine (The OUMERE Routine). Here we summarize one-week histologic observations from an internal explant experiment and direct readers to the full methods outlined previously (Part 1).

Materials & Methods

Study design

Design: Exploratory, parallel explant comparison (n=1 per condition in this pilot run).
Duration: 7 consecutive days.
Treatments:
- Experimental: Topical application of No. 9 Daily Liquid Exfoliant once daily.
- Control: Topical application of deionized water (DI H₂O) once daily.

Explant source & handling

Human skin explants (female, 45 years, abdomen) maintained in recommended growth medium and incubated at 37 °C, 5% CO₂ as described in Part 1 (methods).

Parameter	Details
Sex / Age	Female / 45 years
Anatomical site	Abdomen
Culture	CO₂ incubator, 37 °C; medium refreshed daily
Treatment timing	Once daily, ~10:00 AM, 7 days

Histology

Embedding: Resin embedding following dehydration steps.
Sectioning: ~1000 µm sections prepared for light microscopy.
Staining: Toluidine blue (affinity for acidic tissue components; commonly accentuates collagen-associated structures in this context).
Imaging: Bright-field microscopy; qualitative assessment.

Results

Experimental sample (No. 9) toluidine blue staining with dense blue fibers and visible nuclei — **Figure 1.** Experimental (No. 9) explant after 7 days. Toluidine blue staining shows a visually collagen-rich appearance with conspicuous fibers and cellular nuclei.

Control sample (water) with lighter, sparser staining and fewer visible structures — **Figure 2.** Control (DI H₂O) explant after 7 days. Lighter/two-tone staining with fewer discernible fibers and cells across comparable fields.

Qualitative observations

Staining intensity: Darker toluidine blue signal in the No. 9 sample versus control, consistent with greater collagen-associated staining.
Tissue complexity: The No. 9 sample exhibited visually higher density of fibers and more conspicuous nuclei; the control appeared comparatively sparse.
Overall appearance: The No. 9 sample presented a more architecturally complex field, suggestive of preserved tissue density during the experimental period.

Discussion

Within one week, daily topical No. 9 was associated with a qualitatively collagen-rich, more complex histologic appearance relative to water control. Given toluidine blue’s affinity in this protocol, darker staining is consistent with increased presence or preservation of collagen-associated structures. These observations align with the proposed mechanistic role of controlled acidic turnover—supporting extracellular matrix maintenance by normalizing desquamation and mitigating inflammatory stressors when formulated without sensitizers.

While exploratory, these findings complement OUMERE’s barrier-first guidance and field results reported by customers in longer-term usage surveys (No. 9 2-year survey) and are congruent with our broader research program (e.g., essential oil sensitization analysis; HA water-binding study).

Limitations

Sample size: Pilot run (n=1 per condition) limits inference; results are qualitative.
Duration: One week; does not address longer-term remodeling dynamics.
Quantitation: No blinded morphometrics, stereology, or biochemical collagen assays (e.g., hydroxyproline) in this run.
Section thickness: ~1000 µm; future work will include additional sectioning/staining modalities (e.g., Masson’s trichrome, picrosirius red under polarized light) and thinner sections for finer resolution.
Generalizability: Single donor/explant site; inter-individual variability expected.

Conclusions

In this exploratory histologic comparison, one week of daily No. 9 application was associated with a qualitatively collagen-rich, more complex architecture versus water control. These preliminary findings support continued investigation with larger sample sizes, quantitative endpoints (TEWL, erythema index, image analysis), and extended durations.