Whether dry or oily, dandruff affects a large proportion of the population, either intermittently or persistently. It presents as the formation of small flakes visible on the scalp and hair. However, contrary to popular belief, it is not associated with poor hygiene. Multiple biological and environmental factors contribute to its onset. Continue reading to gain a better understanding of the causes of dandruff.
What are the causes of dandruff?
Summary
Published on July 26, 2022, updated on September 18, 2025, by Sandrine, Scientific Editor — 9 min of reading
Themes:
Dandruff appears as a result of an accelerated skin turnover combined with abnormal desquamation, meaning that dead cells are produced in excessive quantities. Since the epidermal cells are not sufficiently mature, they remain clumped together and detach in clusters: dandruff flakes. This process results from various causes.
Overview of the relationships between dandruff, host demographics, physiological conditions and microorganisms. The colour of the arrows corresponds to the relationship: positive (red), negative (blue) or unique (black).
Source: ZHANG M. & al. Dandruff is associated with the conjoined interactions between host and microorganisms. Scientific Reports (2015).
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Cause No. 1 of dandruff: An imbalance in the microbiota.
Like the skin, the scalp is a living ecosystem inhabited by billions of micro-organisms that coexist: bacteria, fungi and, to a lesser extent, viruses and mites. This community forms the scalp microbiota, whose balance is essential for maintaining healthy skin. Disruption of this equilibrium can lead to the appearance of dandruff in the hair.
A study led by ZHANG and his team in 2015 provides illuminating insights on this topic by sequencing the DNA of the microorganisms present on the scalp of 363 volunteers, with or without dandruff. The researchers showed that two bacterial genera dominate this ecosystem: Cutibacterium (formerly known as Propionibacterium) and Staphylococcus. Normally, these two populations coexist and regulate each other. However, in cases of dandruff, this balance is disrupted: Cutibacterium, decreases drastically, while Staphylococcus proliferates. Moreover, the researchers demonstrated that the severity of dandruff was directly correlated with this shift: the higher the proportion of Staphylococcus increases, the more visible the flakes become.
Distribution of the bacterial population according to the presence or absence of dandruff.
Source: ZHANG M. & al. Dandruff is associated with the conjoined interactions between host and microorganisms. Scientific Reports (2015).
With regard to fungi, the genus Malassezia is also involved in the onset of dandruff. This lipophilic yeast is naturally present in the majority of individuals. Among its species, Malassezia restricta and Malassezia globosa dominate the scalp. However, not all strains have the same impact. Certain variants of M. restricta are strongly associated with the presence of dandruff, whereas others appear to be neutral, or even protective. This finding highlights the importance of intra-species differences, and explains why some individuals can harbour large amounts of Malassezia without developing dandruff in their hair.
Distribution of the fungal population according to the presence or absence of pellicles.
Source: ZHANG M. & al. Dandruff is associated with the conjoined interactions between host and microorganisms. Scientific Reports (2015).
Another key point: bacterial and fungal communities do not appear to act synergistically, but rather independently. More specifically, it is not necessarily the direct interactions between bacteria and fungi that trigger dandruff, but rather the shifts in balance inherent to each group. However, the dynamics between Cutibacterium and Staphylococcus could play a role. Indeed, Cutibacterium produces free fatty acids and bacteriocins capable of limiting the growth of Staphylococcus. When this protective population declines, the scalp becomes more favourable to the proliferation of Staphylococcus, and thus to dandruff.
It is therefore not the presence or absence of a particular type of microorganism that explains dandruff, but an imbalance of the scalp microbiota.
Cause No. 2 of dandruff: An alteration in sebum production.
Sebum is often singled out when it comes to dandruff. This lipid film, secreted by the sebaceous glands, nevertheless has a vital protective function : it lubricates the scalp, maintains its hydration and forms a natural barrier against external aggressions. However, as is often the case in biology, balance is crucial: too little sebum weakens the skin, while too much disrupts the cutaneous ecosystem.
The aforementioned study by ZHANG also analysed the relationship between sebum and dandruff. The researchers found that sebum production varies with age: it reaches its highest levels between 20 and 39 years, then tends to decrease after 40. At first glance, one might expect younger people to be more prone to dandruff. However, the opposite is observed: older adults often exhibit more flakes, despite producing less sebum. This paradox shows that sebum alone is not the direct cause, but works in interaction with the skin microbiota and barrier.
The effect that sebum depends primarily on its composition. Rich in triglycerides and wax esters, it serves as a genuine source of nutrients for lipophilic micro-organisms, notably yeasts of the genus Malassezia. These possess lipase enzymes capable of hydrolysing the triglycerides in sebum and releasing free fatty acids. Among these, certain unsaturated fatty acids are known to be irritants: they disrupt the cohesion of corneocytes in the stratum corneum and increase the permeability of the skin barrier. Consequently, the skin is weakened, local inflammation ensues and desquamation intensifies.
Sebum also influences the bacterial population of the scalp. For example, Cutibacterium uses certain lipids as energy substrates. Its presence, beneficial under balanced conditions, is associated with the production of organic acids and antimicrobial compounds that limit the growth of competing bacteria such as Staphylococcus. An imbalance in the composition of sebum can thus disadvantage some bacterial populations in favour of others, indirectly contributing to the development of dandruff.
Finally, beyond its composition, sebum also acts by modulating transepidermal water loss. Indeed, a deficiency or poor quality of sebum can increase water loss through the epidermis, further compromising the skin barrier. The study shows that the regions of the scalp with elevated transepidermal water loss are also those where dandruff is most pronounced.
Sebum should not be considered an isolated factor but rather as a modulator of scalp equilibrium.
Cause No. 3 of dandruff: Individual and genetic predisposition.
While an imbalance in the cutaneous microbiota and the quantity and quality of sebum are major factors, not everyone reacts to these disturbances in the same way. The emergence of dandruff also depends on characteristics intrinsic to the individual, whether physiological, genetic or related to local variations on the scalp.
ZHANG’s study shows that age influences the onset of dandruff. Adults aged 40 to 59 generally exhibit more dandruff than younger individuals, despite lower sebum production. This phenomenon can be explained by several skin ageing–related factors : the skin barrier becomes less effective, natural hydration diminishes, and the composition of the microbiota evolves over time. Taken together, these changes make the scalp more susceptible to inflammation and flaking.
| Volunteers | Dandruff score (0-8) | Sebum (μg/cm²) |
|---|---|---|
| Volunteers aged 20 to 39 years (n = 96) | 1 | 98 |
| Volunteers aged 40 to 59 years (n=78) | 2 | 70 |
Relationship between dandruff score, age and sebum production.
Source: ZHANG M. & al. Dandruff is associated with the conjoined interactions between host and microorganisms. Scientific Reports (2015).
The genetics also influences the skin’s response. Certain individual variations in sebum lipid composition, cytokine production or skin barrier integrity can make some people more prone to irritation or microbiome imbalances. Moreover, Zhang’s study highlights that the mere presence of Malassezia is not sufficient to cause dandruff: it is the specific strains and their interactions with the scalp that matter. Some individuals tolerate large populations of Malassezia without symptoms, whereas others develop pronounced flaking at similar levels.
Individual susceptibility, shaped by genetic heritage as well as by each person’s physiological and immunological history, is a factor to consider in the development of dandruff.
Note : Stress is often cited as an exacerbating factor in dandruff, but the direct evidence of a link remains limited. Some studies, particularly among adolescents, have not demonstrated a direct association between stress levels and the appearance of dandruff. Nevertheless, it is true that stress can influence scalp health by modulating sebaceous gland activity, a factor involved in the development of dandruff. Further studies are therefore required to conclude on the influence of stress on the appearance of dandruff in hair.
Sources
DAWSON T. L. & al. Three etiologic facets of dandruff and seborrheic dermatitis: Malassezia fungi, sebaceous lipids, and individual sensitivity. Journal of Investigative Dermatology Symposium Proceedings (2005).
WIKRAMANAYAKE C. & al. Seborrheic dermatitis and dandruff: A comprehensive review. Journal of Clinical and Investigative Dermatology (2015).
ZHANG M. & al. Dandruff is associated with the conjoined interactions between host and microorganisms. Scientific Reports (2015).
SHARMA V. K. Comparison of healthy and dandruff scalp microbiome reveals the role of commensals in scalp health. Frontiers in Cellular and Infection Microbiology (2018)
JEGOU-PENOUIL M.-H. Les pellicules. Dermato-info (2019).
LIANA D. F. & al. The relationship of stress level to the incidence of pityriasis capitis (dandruff) in students at SMK Panca Karsa Sungai Pinyuh. Enrichment: Journal of Multidisciplinary Research and Development (2023).
