What actually causes dandruff?

Understanding Malassezia, your scalp microbiome, and why shampoos often only work temporarily.

Dandruff is one of the most common scalp concerns in the world. Dermatological studies estimate that up to 50% of adults experience dandruff at some point in their lives. Yet despite the prevalence, many people still misunderstand what dandruff actually is and why it keeps coming back.

For decades, dandruff has been treated mainly with medicated shampoos designed to remove flakes or suppress yeast growth during washing. While these products can temporarily improve symptoms, many people notice that the flakes return shortly after stopping treatment.

Why does this happen?

To understand dandruff properly, we need to look beyond the flakes themselves and examine what is happening in the scalp ecosystem — especially the role of a naturally occurring yeast called Malassezia.

The hidden driver of dandruff: Malassezia

Dandruff is not simply dry scalp. It is a biological interaction between your scalp microbiome, skin barrier, and a yeast called Malassezia.

What is Malassezia?

Malassezia is a genus of lipid-dependent yeast that naturally lives on human skin. It is particularly abundant in areas rich in sebaceous glands such as the scalp, face, and upper torso.

Scientists have identified more than 14 species of Malassezia on human skin, with Malassezia globosa and Malassezia restricta being the most strongly associated with dandruff.

Importantly, Malassezia is not an infection. It is part of the normal skin microbiome. Most people carry it without problems. However, under certain conditions, the yeast can trigger irritation and excessive skin shedding. This is when dandruff appears.

Key research

  • Malassezia species are present on the scalp of nearly all adults but increase in dandruff-affected individuals.
    (Gupta & Foley, Journal of the American Academy of Dermatology, 2015)
  • M. globosa and M. restricta dominate the scalp microbiome in dandruff conditions.
    (Findley et al., Nature, 2013)

How Malassezia triggers dandruff

The key to understanding dandruff lies in how the yeast interacts with scalp oils. Your scalp produces sebum, a mixture of lipids that protects the skin and hair. Malassezia feeds on these lipids.

When the yeast metabolizes sebum, it produces fatty acid byproducts, particularly oleic acid. For many people, this molecule irritates the scalp.

The chain reaction

The dandruff process typically follows four steps:

1. Yeast feeds on scalp oils

Malassezia consumes lipids from sebum.

2. Irritating fatty acids are produced

During metabolism, the yeast releases oleic acid and other metabolites.

3. Skin barrier becomes disrupted

Oleic acid can penetrate the outer skin layer and weaken the stratum corneum, the scalp's protective barrier.

4. Accelerated skin turnover

The scalp reacts with inflammation and rapid shedding of skin cells, producing visible flakes. Healthy scalp cells normally renew every 28 days. In dandruff conditions, this cycle can accelerate to 7–10 days, meaning immature cells clump together and appear as flakes.

Supporting evidence

  • Oleic acid has been shown to induce dandruff-like flaking in susceptible individuals.
    (DeAngelis et al., Journal of Investigative Dermatology, 2005)
  • Individuals with dandruff show increased scalp barrier disruption and inflammatory markers.
    (Turner et al., International Journal of Cosmetic Science, 2012)

Dandruff is a scalp ecosystem problem

For a long time, dandruff was viewed simply as a fungal issue. But modern research shows that it is better understood as an imbalance in the scalp ecosystem.

This ecosystem includes three interacting elements:

  1. The microbiome (yeasts and bacteria)
  2. The skin barrier
  3. The immune response of the scalp

When these elements are balanced, the scalp stays calm and flake-free. When they become disrupted, dandruff can develop.

The scalp microbiome

Your scalp hosts a complex community of microorganisms. The most common include:

  • Malassezia yeasts
  • Cutibacterium acnes
  • Staphylococcus species

Research has shown that dandruff is associated with changes in the relative abundance of these microbes, not just an increase in yeast.

For example:

  • Dandruff scalps often show higher Malassezia populations
  • Beneficial bacteria may decrease
  • Skin barrier lipids may become altered

This shift is sometimes referred to as microbial dysbiosis.

Scientific insight

  • Dandruff scalps show altered microbial diversity and increased fungal dominance.
    (Clavaud et al., PLoS ONE, 2013)

Why some people get dandruff and others don't

If Malassezia lives on nearly everyone's scalp, why do only some people develop dandruff? The answer lies in individual sensitivity.

Several factors influence how the scalp reacts to yeast metabolites.

1. Skin barrier strength

People with weaker scalp barriers are more susceptible to irritation. Barrier dysfunction allows oleic acid to penetrate deeper into the skin.

2. Sebum production

Oily scalps produce more lipids, providing more food for yeast. This is why dandruff often peaks during puberty and adulthood, when sebum production increases.

3. Individual immune response

Some individuals have a stronger inflammatory reaction to yeast byproducts.

4. Environmental triggers

Factors that can worsen dandruff include:

  • Stress
  • Cold weather
  • Hormonal changes
  • Harsh haircare products
  • Overwashing or underwashing

Why dandruff shampoos often work, but only temporarily

Most anti-dandruff products today are rinse-off shampoos containing antifungal ingredients. Common active ingredients include:

  • Ketoconazole
  • Selenium sulfide
  • Piroctone olamine
  • Zinc-based antifungals (previously Zinc Pyrithione in many regions)

These ingredients reduce yeast populations on the scalp. And they often work, at least temporarily. So why does dandruff return so frequently?

The short-contact problem

Shampoo is typically in contact with the scalp for 30 to 90 seconds before being rinsed away. Even if an active ingredient reduces yeast during washing, the microbiome quickly re-establishes itself afterward. This means the underlying scalp environment may remain unchanged.

Symptom vs. ecosystem treatment

Most traditional shampoos address symptoms:

  • removing flakes
  • suppressing yeast temporarily

But they rarely address the broader scalp ecosystem balance, including barrier health and long-term microbial regulation.

As a result, many users experience a familiar cycle:

  1. Shampoo works for a few weeks
  2. Flakes improve
  3. Product use stops
  4. Dandruff gradually returns

The emerging shift: scalp care beyond shampoo

As the scalp care category evolves, dermatology and cosmetic science are moving toward a more holistic approach.

Instead of treating dandruff only during washing, newer approaches focus on:

  • Restoring the scalp microbiome balance
  • Strengthening the skin barrier
  • Reducing yeast activity over longer contact periods

This has led to increasing interest in leave-in scalp treatments.

Unlike shampoos, leave-in products remain on the scalp for hours, allowing active ingredients to work continuously. In skin care, this principle is already well established. We don't wash off moisturizers or serums after one minute — we leave them on the skin so they can act over time. Scalp care is beginning to follow the same logic.

A new generation of dandruff solutions

Recent cosmetic science developments are exploring bioactive molecules that can help regulate the scalp ecosystem more precisely. Among these innovations are bioactive peptides.

Peptides are short chains of amino acids that can interact with biological systems in highly targeted ways.

In scalp care research, certain peptides are being investigated for their ability to:

  • reduce yeast activity
  • support microbiome balance
  • calm inflammation
  • help strengthen the skin barrier

Because peptides are highly specific biological signals, they represent a promising direction beyond traditional antifungal approaches.

A new perspective on dandruff care

Understanding dandruff as an ecosystem imbalance rather than just a fungal problem changes how we think about treatment.

Effective scalp care may require:

  • addressing yeast activity
  • supporting the scalp barrier
  • maintaining microbiome balance
  • allowing active ingredients enough time to work

This perspective is at the core of emerging scalp science — and of next-generation solutions like Calmbay. Rather than relying only on short-contact shampoos, Calmbay was developed as a leave-in peptide scalp treatment designed to work longer on the scalp ecosystem.

By targeting the biological drivers behind dandruff while respecting the scalp's natural balance, this approach reflects the evolving understanding of dandruff in modern dermatological research.

Key takeaways

  • Dandruff is primarily driven by the yeast Malassezia, which feeds on scalp oils.
  • The yeast produces fatty acids like oleic acid, which can irritate the scalp and disrupt the skin barrier.
  • This leads to accelerated skin cell turnover, resulting in visible flakes.
  • Dandruff is best understood as a scalp ecosystem imbalance involving microbes, skin barrier, and immune response.
  • Traditional shampoos often work temporarily because they have short contact time.
  • Newer approaches focus on longer-acting scalp treatments that help restore balance.

If you struggle with recurring dandruff, the solution may not be washing harder, but understanding and caring for the scalp ecosystem itself.

Looking for more detailed scientific information?

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A closer look on the science

What are peptides?

Peptides are short chains of amino acids, the smallest building blocks of proteins. They are not new: they occur naturally in the body and direct processes such as skin repair, cell communication and immune responses.

In premium skincare, peptides have been a gold standard for more than twenty years. They are valued for their precision: they communicate with specific cells or structures without overloading the skin. That is the difference from broad-spectrum ingredients that target everything, including what does not need
to be touched.

What does the Calmbay peptide do for the microbiome balance?

The most sustainable treatment for dandruff is not one that makes the scalp sterile. It is one that brings the microbiome back into balance so the skin can maintain itself.

The scalp microbiome is a delicate ecosystem. A healthy scalp has a richer, more diverse microbial community. With dandruff, diversity decreases: Malassezia
restricta dominates, while beneficial species such as Cutibacterium acnes fade into the background. The result is a dysregulated system that repeatedly falls out of balance, even after treatment.

Conventional anti-dandruff treatments reduce Malassezia, but do not always positively influence the broader microbiome composition. Once treatment stops, the imbalance returns — sometimes more quickly, because beneficial micro-organisms have also been disrupted.

hLF1-11 works with greater selectivity. By curbing Malassezia overgrowth through direct cell wall interaction and iron sequestration, while simultaneously
strengthening local immunity, it creates the conditions under which the microbiome can restore itself. The skin does not become dependent on an
external agent — it is empowered to regain its own regulatory capacity.

How does Malassezia disrupt the balance on your scalp?

On a healthy scalp, Malassezia is always present. It is a lipophilic yeast, meaning it feeds on the fatty acids in sebum. In a healthy state, Malasseziaexists in balance with other micro-organisms, including Cutibacterium acnes and Staphylococcus epidermidis.

With dandruff, that balance shifts. Malassezia restricta grows excessively, while Cutibacterium acnes declines. This is not coincidental: C.acnes produces propionic acid, which helps regulate Malassezia overgrowth. When that bacterium declines, the scalp loses part of its own self-regulatory capacity.

Inovergrowth, Malassezia metabolises sebum and produces free fatty acids such as oleic acid in the process. These fatty acids irritate the skin barrier, trigger inflammatory responses and accelerate the rate at which skin cells divide. The result: the rapid flaking we see as dandruff, combined with itching
and sometimes redness.

The solution is not to eliminate Malassezia entirely. It is always present and plays a role in the ecosystem. The solution is to restore balance: curbing the
overgrowth, supporting the skin barrier and creating the conditions in which the microbiome can self-regulate again.

That is precisely what the active ingredient in Calmbay does.

What is HLF1-11?

hLF1-11 is the name of the peptide at the core of the Calmbay formula. The name refers to the amino acid sequence.

Lactoferrin is a protein the human body produces itself. It is present in breast milk, saliva, tears and mucous embranes, wherever the body meets the outside world and needs to defend itself. Lactoferrin has strong antimicrobial and anti-inflammatory properties, and plays an important role in innate immunity.

Researchers discovered that much of lactoferrin's potency resides in a specific fragment. This fragment was found to possess broad antifungal activity, antimicrobial properties and immunomodulatory effects.

hLF1-11 is the synthetic, stable reproduction of this fragment. That may sound technical, but the implication is simple: it is an active ingredient the body recognises as its own. Not a foreign chemical compound, but a molecule inspired by what nature has already designed.

In the Calmbay Anti-Dandruff Scalp Treatment, this peptide acts directly on the fungal cells that cause dandruff and simultaneously on the scalp's own immune system.

How exactly does the Calmbay peptide work on the yeast cells?

hLF1-11 works through multiple mechanisms simultaneously. That is what sets it apart from conventional anti-dandruff treatments, which typically operate through a single mode of action.

Direct action on the cell wall
hLF1-11 binds to the cell wall of Malassezia and disrupts its integrity. This process leads to cytolysis: the rupture and death of the fungal cell. The yeast cannot defend itself against this mechanism, because the
peptide targets fundamental structures in the cell wall.

Depriving the environment of iron
Lactoferrin-derived peptides bind iron. Malassezia requires iron for growth and virulence. By sequestering iron from the yeast's immediate environment its growth is slowed, without placing any burden on the skin itself.

Strengthening local immunity
Beyond direct antifungal action, hLF1-11 modulates the skin's immune response. It activates monocytes and macrophages — immune cells that can themselves clear fungal cells — and regulates inflammatory signals so the skin remains calmer.

Synergy with other active ingredients
Laboratory research shows that hLF1-11 works synergistically with other antifungal agents: the combined effect is greater than the sum of its parts. This makes the peptide exceptionally well-suited as a core ingredient in a multi-active formula.

Together,these mechanisms deliver something conventional products rarely offer: targeted, lasting action on the cause, not the symptom.

Why are peptides now central to scalp care?

The scalp is not an extension of the hair: it is skin, with its own microbiome, its own barrier function and its own vulnerability to imbalance. The challenges are specific, and call for specific active ingredients.

Calmbay uses a bio-identical peptide that acts directly on the root cause of dandruff: the overgrowth of Malassezia yeast and the associated microbiome disruption.