What is dandruff and what causes it?
Dandruff is a persistent and recurrent disease of the scalp, which is characterised by the formation of white flakes. Research shows that disruption of the microbiome of the scalp is one of the main causes of dandruff. The disorder affects about half of the world population, regardless of gender or ethnic background.
When the barrier function of the scalp is disrupted, pityriasis capitis or dandruff occurs. In the healthy scalp, cell renewal proceeds at a normal pace whereas in a disturbed scalp it happens much faster. Simultaneously, a larger amount of dead skin cells are secreted in the form of white flakes.
In most cases it is a combination of several factors that disrupts the barrier function of the scalp: alteration in the rate of cell regeneration, reduced hydration of the scalp, excessive sebum production, dryness of the scalp as a result of an alteration of the natural moisturising factors. This creates a permanent recurring infection.
Disruption of the microbiome
Research has shown that the balance between bacteria and fungi on the scalp is disrupted in patients who suffer from dandruff. Dandruff scalps have a higher presence of the fungus Malassezia restricta and of the bacterium Staphylococcus. And although everybody has these bacteria and fungi naturally, it’s when they are out of balance that problems can occur. People who suffer from dandruff have significantly higher ratios of Malassezia to Propionibacterium and Propionibacterium to Staphylococcus.
Importance of Malassezia
The fungus Malassezia lives on everybody’s skin and for a long time it was considered as a benign fungus. However, it can cause inflammatory reactions that may lead to symptomatic skin diseases (such as dandruff) and to infections of the bloodstream. Researchers have proposed several hypotheses to explain the pathogenic mechanisms of this fungus, but these have not yet been confirmed.
Although the production of dandruff is certainly associated with the presence of Malassezia, the importance of Malassezia and the participation of Staphylococcus and Propionibacterium related to dandruff remain unclear.
It seems that this disturbance of the scalp microbiota may be treated in a natural way. Restoring this balance could prevent the formation of dandruff.
- Grice, E.A. & Segre, J.A., 2011. The skin microbiome. Nature reviews. Microbiology, 9(4), pp.244–53.
- Wang, L. et al., 2015. Characterization of the major bacterial-fungal populations colonizing dandruff scalps in Shanghai, China, shows microbial disequilibrium. Experimental dermatology, 24(5), pp.398–400.