What causes dandruff?

Causes of Dandruff

Dandruff is primarily caused by the lipophilic yeast Malassezia species (particularly Malassezia globosa), combined with sebaceous secretions and individual sensitivity. 1

Primary Causative Factors

1. Fungal Component

• Malassezia fungi (formerly known as Pityrosporum ovale) are the primary causative organisms 2, 1
• Most common species involved:
  • Malassezia globosa (67.15% of cases)
  • Malassezia furfur (21.70% of cases)
  • Malassezia restricta (12.15% of cases) 3
• Mechanism: These lipophilic yeasts metabolize sebaceous triglycerides, releasing irritating free fatty acids (particularly oleic acid) that cause scalp inflammation and accelerated skin cell turnover 1

2. Sebaceous Gland Activity

• Excessive sebum production provides an ideal environment for Malassezia growth 1
• Sebaceous secretions serve as a nutrient source for the fungi
• The interaction between sebum and Malassezia leads to the production of irritating free fatty acids 1

3. Individual Susceptibility

• Not everyone with Malassezia on their scalp develops dandruff
• Individual sensitivity to the free fatty acid metabolites determines whether symptoms develop 1
• This explains why dandruff severity varies significantly between individuals with similar fungal counts

Contributing Factors

Environmental Triggers

• Changes in humidity
• Seasonal changes (often worse in winter)
• Emotional stress 2

Demographic Factors

• Gender: Males are more affected than females (AOR = 2.605) 3
• Age: Greatest prevalence and severity in young men 2, 3
• Hair care practices:
  • Use of hair oils increases risk (AOR = 2.964) 3
  • Use of anti-dandruff shampoo decreases risk (AOR = 2.782) 3

Dermatological Conditions

• Seborrheic dermatitis (more severe form with similar pathophysiology)
• Other inflammatory dermatoses that can mimic or contribute to dandruff:
  • Eczema (atopic dermatitis)
  • Seborrhea (seborrheic dermatitis)
  • Psoriasis 4

Clinical Presentation

• Fine scaling of the scalp resembling dry skin
• Severity ranges from mild to severe scaling
• Often accompanied by itching
• May be aggravated by scratching 2

Differential Diagnosis

When evaluating scalp scaling, it's important to distinguish dandruff from other conditions:

• Tinea capitis: Fungal infection of scalp hair follicles, often with patchy hair loss 4
• Psoriasis: More defined plaques with thicker scale
• Atopic dermatitis: Often with other body involvement and history of atopy 4
• Contact dermatitis: May be irritant or allergic, often with history of exposure to irritants or allergens 4

Management Implications

Understanding the multifactorial nature of dandruff informs effective treatment:

• Antifungal agents: Target Malassezia species (zinc pyrithione, selenium sulfide, ketoconazole) 5
• Keratolytic agents: Help remove scale (salicylic acid, sulfur)
• Anti-inflammatory agents: Reduce inflammation and itching
• Regular shampooing: Helps control both fungal populations and sebum levels 2

Ketoconazole-containing shampoos (Nizoral) have been shown to be particularly effective, with 2% formulations demonstrating 10 times greater antifungal activity than 1% formulations, and 100 times greater activity than other common anti-dandruff shampoos 5.

Prevention Strategies

• Regular use of anti-dandruff shampoos
• Avoiding excessive use of hair oils and styling products
• Stress management
• Wearing fine cotton clothes instead of synthetic materials to reduce scalp irritation 6

Understanding that dandruff results from the interaction of Malassezia fungi, sebaceous secretions, and individual sensitivity provides the foundation for effective management strategies targeting these key pathogenic factors.