7.5 Chemical Exfoliants, Enzymes & Antioxidants

7.5 Chemical Exfoliants, Enzymes & Antioxidants

1. Chemical & Enzymatic Exfoliating Agents

Exfoliating agents accelerate desquamation, refine skin texture, clear follicular congestion, and stimulate basal keratinocyte mitosis.

                                  ┌──────────────────────────────────────────────────────────┐
                                  │               CHEMICAL & ENZYMATIC EXFOLIANTS            │
                                  └────────────────────────────┬─────────────────────────────┘
                                                               │
                ┌──────────────────────────────┼──────────────────────────────┐
                ▼                              ▼                              ▼
 ┌──────────────────────────────┐ ┌──────────────────────────────┐ ┌──────────────────────────────┐
 │ ALPHA HYDROXY ACIDS (AHAs)   │ │  BETA HYDROXY ACIDS (BHAs)   │ │     PROTEOLYTIC ENZYMES    │
 ├──────────────────────────────┤ ├──────────────────────────────┤ ├──────────────────────────────┤
 │ • WATER-SOLUBLE              │ │ • OIL / LIPID-SOLUBLE        │ │ • BIOLOGICAL PROTEIN DIGEST│
 │ • Dissolve corneodesmosome   │ │ • Penetrates follicular pore │ │ • Hydrolyzes surface       │
 │   intercellular lipid glue   │ │   lining and dissolves sebum │   keratin without penetration│
 │ • Glycolic (Sugar Cane, 76MW)│ │ • Salicylic Acid (Willow)    │ • Papain (Green Papaya)      │
 │ • Lactic (Sour Milk, 90MW)   │ │ • Anti-inflammatory/aspirin  │ • Bromelain (Pineapple)      │
 │ • Mandelic (Almonds, 152MW)  │ │ • Gold standard for acne     │ • Pumpkin enzymes            │
 └──────────────────────────────┘ └──────────────────────────────┘ └──────────────────────────────┘

A. Alpha Hydroxy Acids (AHAs — Water-Soluble Desmosome Dissolvers)

AHAs are water-soluble organic carboxylic acids derived from natural sugars. They work by cleaving the calcium ions in corneodesmosomes (the intercellular protein "glue" binding corneocytes together), facilitating rapid surface desquamation:

• Glycolic Acid (Derived from Sugar Cane): The smallest molecular size ($MW = 76\text{ g/mol}$) among all AHAs. Provides deepest, fastest epidermal penetration and highest stimulation of collagen synthesis, but carries the highest potential for stinging, irritation, and erythema.
• Lactic Acid (Derived from Sour Milk / Fermented Dairy): Larger molecule ($MW = 90\text{ g/mol}$) that penetrates more gradually. Uniquely possesses natural humectant properties and stimulates cutaneous ceramide synthesis; ideal for dry, dehydrated, or sensitive skin.
• Mandelic Acid (Derived from Bitter Almonds): The largest common AHA molecule ($MW = 152\text{ g/mol}$). Its large molecular weight provides slow, uniform penetration with minimal erythema. Its unique aromatic ring confers mild lipophilic and antibacterial activity, making it the premier AHA for sensitive acne-prone skin and Fitzpatrick phototypes IV–VI prone to post-inflammatory hyperpigmentation (PIH).
• Other AHAs: Tartaric Acid (grapes), Malic Acid (apples), and Citric Acid (citrus fruits; also serves as a formulation pH buffer).

B. Beta Hydroxy Acids (BHAs — Oil-Soluble Follicular Cleansers)

• Salicylic Acid (Derived from Willow Bark & Sweet Birch):
  • Unlike water-soluble AHAs, salicylic acid is lipid-soluble (lipophilic).
  • It can dissolve through surface sebum and migrate directly into the sebaceous follicular infundibulum / pore lining, dissolving trapped sebum, oxidised debris, and retained dead keratinocytes.
  • Salicylic acid is structurally related to aspirin (acetylsalicylic acid) and retains potent anti-inflammatory, antimicrobial, and analgesic properties, making it the clinical gold standard for acne vulgaris and comedonal congestion.
  • Contraindication: Clients with known aspirin (salicylate) allergies must never receive salicylic acid products.

C. Proteolytic Enzymes (Biological Protein Catalysts)

• Enzymes are biological protein catalysts that digest and hydrolyze keratin proteins on the outer stratum corneum into individual amino acids.
• They operate exclusively on non-living dead keratin at the skin surface and do not penetrate into living epidermal layers, making them ideal for sensitive skin, rosacea, and reactive skin types.
• Papain: Extracted from green papaya fruit.
• Bromelain: Extracted from pineapple stem and juice.
• Pumpkin & Pomegranate Enzymes: Fermented fruit extracts rich in proteases, carotenoids, and vitamins.

2. Antioxidants & Cellular Defense

Free radicals are highly reactive, unstable molecules containing an unpaired valence electron, generated by solar ultraviolet radiation, airborne pollution, ozone, cigarette smoke, and cellular metabolic respiration. Free radicals attack cell membranes through lipid peroxidation, cross-link dermal collagen and elastin fibers (causing premature elastosis and wrinkling), and induce nuclear DNA mutations.

Free Radical (Unpaired Electron) + Antioxidant (Electron Donor) ───> Stable Molecule + Quenched Radical

Major Cosmetic Antioxidants

• Vitamin C (L-Ascorbic Acid):
  • The primary water-soluble physiological antioxidant in human tissue.
  • Essential cofactor for prolyl and lysyl hydroxylase enzymes in collagen synthesis.
  • Potent tyrosinase inhibitor that lightens hyperpigmentation and evens skin tone.
  • Unstable and easily oxidized by light/air; requires an acidic formulation pH (<3.5) or conversion to stable derivatives (Tetrahexyldecyl Ascorbate, Sodium Ascorbyl Phosphate, Magnesium Ascorbyl Phosphate).
• Vitamin E (Tocopherol / Tocopheryl Acetate):
  • The primary lipid-soluble antioxidant protecting cellular membrane lipids from peroxidation.
  • Works synergistically with Vitamin C (Vitamin C chemically reduces and regenerates oxidized Vitamin E).
• Ferulic Acid: Plant-derived phenolic antioxidant that stabilizes Vitamin C and Vitamin E, doubling their photoprotective efficacy against UV-induced erythema.
• Coenzyme Q10 (Ubiquinone): Fat-soluble antioxidant residing in mitochondrial membranes that supports cellular ATP synthesis and protects against collagenase degradation.
• Resveratrol: Potent polyphenol found in grape skins that stimulates cellular longevity pathways (sirtuins) and quenches oxidative stress.
• Green Tea Extract (EGCG - Epigallocatechin Gallate): Polyphenol providing exceptional antioxidant, anti-inflammatory, and sebostatic (oil-reducing) benefits.

3. Concentration, pH and Free Acid: Why Two "20% Glycolic" Products Behave Differently

A chemical exfoliant's strength is never one number. Three interact:

• Total acid concentration — how much acid is in the bottle by weight.
• pH — how much of that acid is present in its active, un-neutralized form. A lower pH means more free acid and more aggressive exfoliation.
• Free acid value — the percentage actually available to act, which the formulator adjusts by buffering, that is, partially neutralizing the acid with an alkaline agent.

A 20% glycolic solution at pH 3.0 and a buffered 20% glycolic gel at pH 4.0 are both truthfully labeled 20% and behave nothing alike. Never judge a professional exfoliant on percentage alone; read the pH beside it.

The benchmarks the industry works to come from the Cosmetic Ingredient Review Expert Panel, and they are the origin of the figures state rules quote:

Oklahoma's chemical-exfoliation rule tracks the professional row of this table, which is why the figures appearing in OAC 175:10-7-29 are 30% and a pH of 3 rather than some other pair of numbers.

The photosensitivity rule

Alpha hydroxy acids raise the skin's sensitivity to ultraviolet light while in use and for about a week after use stops. The recommended Sunburn Alert labeling advises consumers to use a sunscreen, wear protective clothing and limit sun exposure during use and for a week afterward. In practice this means no exfoliation series without a daily broad-spectrum sunscreen commitment from the client, and no aggressive exfoliation booked immediately before a beach holiday or an outdoor event.

Getting enzymes to actually work

Enzymes are proteins, so they are condition-dependent. They are catalytically active only within a limited pH and temperature range, and they require moisture — an enzyme mask that has dried on the skin has stopped working. That is why enzyme treatments are held under steam, a warm towel or a humidity dome for their five-to-fifteen-minute dwell, and why a papain product allowed to dry hard delivers far less exfoliation than the label promises.

4. Handling Antioxidants So They Are Still Active

An antioxidant is by definition a molecule that oxidizes readily, which means it degrades in the bottle as willingly as it works on the skin.

• L-ascorbic acid is typically formulated at 10% to 20% and needs a pH below roughly 3.5 to penetrate. It oxidizes on exposure to light, air and heat, turning yellow and then brown. A browned serum has lost potency and should be discarded rather than used up.
• Packaging is part of the formula. Opaque, airless or single-dose packaging protects vitamin C, retinoids and polyphenols. A wide-mouth jar does not.
• Combinations outperform singles. Vitamin C regenerates oxidized vitamin E and ferulic acid stabilizes both, which is why the classic photoprotective serum pairs L-ascorbic acid with vitamin E and ferulic acid rather than using any one alone.
• Antioxidants prevent rather than repair. They quench free radicals before oxidative damage occurs, so they belong in the morning routine underneath sunscreen rather than being treated as a corrective night product.