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leaves and flowers of self-heal (Prunella vulgaris)

Dermatological Mechanisms, Barrier Function, and Phytochemical Applications

Scope: Western dermatology, skin physiology, phytochemical mechanisms for skin support.

Table of Contents

  1. Skin Architecture and Barrier Function
  2. Wound Healing Physiology
  3. Inflammatory Skin Conditions
  4. Herbal Mechanisms: Calendula
  5. Herbal Mechanisms: Oats
  6. Clinical Applications

Skin Architecture and Barrier Function

Epidermal Structure

The epidermis is stratified squamous epithelium with four distinct layers (five in thick skin):

1. Stratum Basale (Basal Layer):

2. Stratum Spinosum (Spinous Layer):

3. Stratum Granulosum (Granular Layer):

4. Stratum Corneum (Horny Layer):

Barrier Function: The “Brick and Mortar” Model

Corneocytes (“Bricks”):

Structure:

Keratin filament-filaggrin matrix:

Filaggrin breakdown:

Lipid Matrix (“Mortar”):

Composition (ratio ~3:1:1 by weight):

Lipid organisation:

Lipid synthesis and processing:

In stratum granulosum:

At stratum granulosum/corneum interface:

Formation of lipid lamellae:

Barrier Functions

1. Permeability Barrier:

Barrier disruption consequences:

2. Antimicrobial Barrier:

Antimicrobial peptides (AMPs):

Major AMP families:

Mechanisms:

Dysregulation:

3. Immunological Barrier:

Skin immune cells:

Immune surveillance:

Wound Healing Physiology

Phases of Cutaneous Wound Healing

Phase 1: Hemostasis (Immediate, minutes-hours)

Vascular response:

Growth factor release:

Phase 2: Inflammation (Hours to days 3-5)

Purpose: Clean wound, prevent infection, initiate repair

Cellular infiltration:

Early (hours):

Later (days 2-3):

Cytokine profile:

Prolonged inflammation = chronic wound

Phase 3: Proliferation (Days 4-21)

Three concurrent processes:

A. Granulation Tissue Formation:

Components:

Fibroblast activity:

Angiogenesis:

Appearance: Pink, granular tissue filling wound bed

B. Re-epithelialisation (Epithelialisation):

Keratinocyte response to injury:

Within hours:

Keratinocyte migration:

Proliferation:

Basement membrane reformation:

Completion: When migrating fronts meet at wound centre

C. Wound Contraction:

Mechanism:

Importance: Particularly important in large wounds

Phase 4: Remodeling (Weeks to months-years)

Collagen reorganisation:

Scar maturation:

Tensile strength:

Matrix metalloproteinases (MMPs) vs. Tissue inhibitors of metalloproteinases (TIMPs):

Factors Affecting Wound Healing

Local factors:

Systemic factors:

Inflammatory Skin Conditions

Atopic Dermatitis (Eczema)

Pathophysiology:

Barrier dysfunction:

Immune dysregulation:

Inflammation:

Itch-scratch cycle:

Microbial colonisation:

Herbal relevance:

Barrier support:

Anti-inflammatory:

Anti-pruritic:

Psoriasis

Pathophysiology:

Hyperproliferation:

Immune activation:

Inflammation:

Vascular changes:

Genetics:

Herbal relevance:

Limited efficacy as monotherapy for moderate-severe psoriasis

Supportive role:

Calendula: Phytochemistry and Mechanisms

Calendula (Calendula officinalis) flower
Calendula (Calendula officinalis)

Detailed Phytochemical Profile

Triterpenoid Saponins:

Major compounds:

Properties:

Triterpenoid Alcohols:

Major compounds:

Properties:

Flavonoids:

Major flavonoids:

Properties:

Carotenoids:

Major carotenoids:

Properties:

Polysaccharides:

Structure: Complex carbohydrates

Properties:

Volatile Oils:

Minor component but contributes antimicrobial activity

Wound Healing Mechanisms

Mechanism 1: Enhanced Granulation Tissue Formation

Triterpenoid saponin effects:

Stimulate fibroblast proliferation:

Enhance collagen synthesis:

Mechanism: Likely involves growth factor signaling (TGF-β, PDGF pathways)

Mechanism 2: Promotion of Epithelialisation

Accelerates re-epithelialisation:

Keratinocyte proliferation:

Keratinocyte migration:

Clinical evidence:

Mechanism 3: Anti-Inflammatory Activity

Primary mechanism: Lipoxygenase (LOX) inhibition

Faradiol is key compound:

Comparative efficacy:

Additional anti-inflammatory mechanisms:

Result: Reduced redness, swelling, pain in inflamed/wounded skin

Mechanism 4: Antimicrobial Activity

Broad-spectrum activity:

Antibacterial:

Antifungal:

Mechanisms:

Mechanism 5: Antioxidant Effects

Carotenoids and flavonoids:

Lipid peroxidation inhibition:

Bioavailability and Formulation

Topical application:

Absorption:

Formulation considerations:

Optimal for wound healing:

Oat Mechanisms: Anti-Pruritic Science

oats (Avena sativa) leaves and seed head close up
Oats (Avena sativa)

Avenanthramides: Unique Oat Compounds

Structure:

Anti-inflammatory mechanisms:

1. Histamine Release Inhibition:

2. Pro-inflammatory Cytokine Suppression:

3. Nitric Oxide Synthase Inhibition:

Beta-Glucans: Protective Polysaccharides

Structure:

Mechanisms:

1. Film Formation:

2. Moisture Retention:

3. Immunomodulation:

Saponins: Gentle Cleansing

Properties:

Clinical Evidence

Atopic dermatitis studies:

Mechanism of bath action:

Clinical Applications and Protocols

Atopic Dermatitis Management

Phase 1: Acute Flare (Days 1-7)

Topical:

Internal:

Phase 2: Maintenance (Ongoing)

Topical:

Internal:

Lifestyle:

Timeline: Improvement usually 2-4 weeks; full control may take 2-3 months

Wound Healing Protocol

Clean wounds only (no active infection requiring antibiotics)

Immediate (Day 1):

  1. Clean wound thoroughly (water, gentle soap if needed)
  2. Apply: Fresh plantain poultice OR honey OR calendula cream
  3. Cover with sterile dressing

Days 2-14 (until epithelialisation complete):

  1. Clean gently daily
  2. Apply calendula salve 2-4x daily
  3. Keep moist (moist wounds heal faster)
  4. Change dressing daily

Remodeling phase (Weeks 2-months):

Infection monitoring:

Safety Considerations

Calendula:

  • Very safe topically
  • Allergic reactions possible (Asteraceae allergy)
  • Always patch test
  • Internal use limited (saponins hemolytic at high doses)

Comfrey:

  • Contains pyrrolizidine alkaloids (hepatotoxic)
  • External use only
  • Not on deep or infected wounds
  • Not on broken skin for extended periods

Plantain:

  • Extremely safe
  • Can use liberally

Oats:

  • Very safe
  • Use plain oats (no added sugars/flavours)

References

Bone, K., & Mills, S. (2013). Principles and practice of phytotherapy: Modern herbal medicine (2nd ed.). Churchill Livingstone.

Guo, S., & DiPietro, L.A. (2010). Factors affecting wound healing. Journal of Dental Research, 89(3), 219-229.

Pazyar, N., Yaghoobi, R., Rafiee, E., Mehrabian, A., & Feily, A. (2013). Skin wound healing and phytomedicine: A review. Skin Pharmacology and Physiology, 26(6), 303-310.

Proksch, E., Brandner, J.M., & Jensen, J.M. (2008). The skin: An indispensable barrier. Experimental Dermatology, 17(12), 1063-1072.

Sur, R., Nigam, A., Grote, D., Liebel, F., & Southall, M.D. (2008). Avenanthramides, polyphenols from oats, exhibit anti-inflammatory and anti-itch activity. Archives of Dermatological Research, 300(10), 569-574.

Disclaimer: Does not represent rongoā Māori methods. For rongoā knowledge, consult Te Paepae Motuhake.

Medical Disclaimer: This guide is for educational purposes only and is not medical advice. Serious wounds, persistent skin conditions, changing moles, or signs of infection require professional medical evaluation. Herbal skin therapies support healing but do not replace dermatological care. Consult qualified healthcare practitioners, especially if pregnant, nursing, taking medications, or having medical conditions.

Note on Pricing: All prices mentioned in this guide are approximate and based on New Zealand suppliers as of December 2025. Prices vary by supplier, season, and market conditions. We recommend checking current prices with your local suppliers.

The Public Herbarium is built on a foundation of scientific integrity, transparency, and care. Research sources are referenced throughout the site wherever possible. Content creation is assisted by AI tools and carefully reviewed for accuracy.