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.