Why do We Get Dandruff?

As mentioned above, dandruff is the result of accelerated cell renewal. This problem is the result of a disorder in the scalp, which can be triggered by several mechanisms:

• A proliferation of fungi of the Malassezia type.

Several studies suggest the pathogenic role of Malassezia fungi in the appearance of dandruff.

Malassezia is a type of yeast that is part of the commensal flora of humans and various animals. These yeasts are lipophilic, meaning that their growth depends on certain fatty acids in the skin. They are mainly found in the seborrheic areas of the body.

Under certain conditions, these yeasts can become pathogenic. Studies have shown the presence of Malassezia on the scalp of people with dandruff. Indeed, Malassezia has a lipase activity, which means that it hydrolyzes the triglycerides present in the sebum, releasing unsaturated fatty acids such as oleic acid and arachidonic acid. The above are the metabolites that cause abnormal differentiation of the keratinocytes. This leads to abnormalities of the stratum corneum such as parakeratosis. Furthermore, the metabolites produced by Malassezia are responsible for the production of pro-inflammatory cytokines by the keratinocytes. Arachidonic acid also produces prostaglandins which are pro-inflammatory mediators.

Note: Parakeratosis a dermatosis characterized by abnormal maturation of keratin. It is manifested by red lesions and scales.

However, the mere presence of Malassezia on the scalp is not enough to cause dandruff. Indeed, many studies have proven that it is the individual predisposition and the interaction of the host with Malassezia that contribute to the formation of dandruff.

• Sebaceous gland activity.

Sebaceous glands are glands attached to the epidermis that secrete sebum. They are located on the entire surface of the body except for the palms of the hands and the soles of the feet. On the scalp, the sebaceous glands are present in very large quantities.

Under hormonal control, the sebaceous glands are very active in producing sebum at the time of puberty. In addition, the rate of sebum production is higher among men. The appearance of dandruff shows a strong temporal correlation with the activity of the sebaceous glands since dandruff generally occurs at the time of puberty. This can be explained by the fact that Malassezia fungi feed on the fatty acids present in the skin, particularly in the sebum.

• Individual predisposition.

In addition to the colonization by Malassezia fungi and the hyperproduction of sebum, there are other factors that contribute to the appearance of dandruff. These factors include genetics, the skin's barrier function and diet.

Some people have a genetic predisposition to dandruff development. Studies on animal and human models have identified dominant and recessive hereditary forms of dandruff. This condition can be lifelong and does not appear to respond to standard treatments.

Dandruff can also be caused by a defective barrier function that results from a disruption of lipid organization and the desquamation process. Studies have found skin barrier abnormalities in the scalp of people with dandruff.

While some people are naturally prone to dandruff, others develop it under the influence of various factors such as emotional stress or an unbalanced diet. Indeed, these factors would favor an over-secretion of sebum, a favorable environment for the development of Malassezia-type yeasts.

There is no single cause of dandruff. The presence of Malassezia yeast, the activity of the sebaceous glands combined with various factors such as diet, stress or genetics determine an individual's susceptibility to developing dandruff.