🦷 Seborrheic Dermatitis/Dandruff Mechanism Simulator

Baseline Scalp — Malassezia as a Normal Resident

Placeholder lead: Malassezia yeast is a normal, harmless scalp resident in most people.

• 3–12: Malassezia species on scalp (Placeholder short caption.)
• 10⁴–10⁶/cm²: Normal yeast density (Placeholder short caption.)
• Normal: Baseline sebum output (Placeholder short caption.)
• Minimal: Baseline flaking (Placeholder short caption.)

Malassezia is a lipophilic commensal yeast

Placeholder: yeast requires external lipids, so it clusters near oily skin.

Balance keeps the scalp asymptomatic

Placeholder: normal sebum and turnover rates keep yeast growth in check.

Placeholder highlight: most scalps carry Malassezia without any visible symptoms.

Excess Sebum Production Creates a Favorable Niche

Placeholder lead: hormones, genetics, and climate can raise sebaceous gland output.

• 2–3×: Sebum increase range (Placeholder short caption.)
• Androgens: Key driver (Placeholder short caption.)
• Puberty–40s: Peak sebum age (Placeholder short caption.)
• High: Gland density (scalp) (Placeholder short caption.)

Sebaceous glands respond to hormonal and individual variation

Placeholder: androgen sensitivity varies, driving individual differences in oiliness.

More sebum means more fuel for yeast growth

Placeholder: richer lipid film lets Malassezia populations expand rapidly.

Placeholder highlight: sebum-rich areas like scalp and face are classic dandruff sites.

Malassezia Metabolizes Sebum Into Irritant Fatty Acids

Placeholder lead: yeast lipases break sebum triglycerides into free fatty acids.

• Lipases: Key enzyme class (Placeholder short caption.)
• Free fatty acids: Byproduct type (Placeholder short caption.)
• Oleic, arachidonic acid: Irritant examples (Placeholder short caption.)
• Accelerated: Yeast growth response (Placeholder short caption.)

Lipase digestion releases irritating unsaturated fatty acids

Placeholder: some fatty acids penetrate skin barrier and provoke irritation.

Byproducts disrupt normal stratum corneum barrier function

Placeholder: barrier disruption sensitizes skin to further irritant exposure.

Placeholder highlight: oleic acid famously triggers flaking in susceptible individuals.

Inflammation Drives Accelerated Epidermal Turnover

Placeholder lead: irritants trigger local inflammation and faster skin cell cycling.

• ~28 days: Normal turnover time (Placeholder short caption.)
• ~7–14 days: Dandruff turnover time (Placeholder short caption.)
• Flaking, redness: Visible sign (Placeholder short caption.)
• ~50% adults: Affected population (Placeholder short caption.)

Faster turnover produces immature, clumping corneocytes

Placeholder: rushed cells shed together as visible clumps instead of single cells.

Local inflammatory signaling reinforces redness and itch

Placeholder: cytokine release sustains irritation and visible scalp redness.

Placeholder highlight: flakes are essentially clumped, immature skin cells shed early.

Antifungal and Cytostatic Shampoos Both Reduce Flaking

Placeholder lead: ketoconazole and zinc pyrithione treat dandruff through different mechanisms.

• Antifungal: Ketoconazole mechanism (Placeholder short caption.)
• Antimicrobial/cytostatic: Zinc pyrithione mechanism (Placeholder short caption.)
• 2–8 weeks: Typical response window (Placeholder short caption.)
• Ongoing use: Maintenance need (Placeholder short caption.)

Ketoconazole lowers Malassezia population directly

Placeholder: antifungal action shrinks yeast numbers, reducing irritant production.

Zinc pyrithione slows turnover without eliminating yeast

Placeholder: cytostatic action calms cell cycling even as yeast levels persist.

Placeholder highlight: both treatments reduce flaking and redness with regular use.