Scalp: What is hyperseborrhea?

The sebaceous glands are exocrine glands located in the dermis responsible for the production of sebum. This is a complex mixture of lipids that plays a crucial role in protecting the scalp and skin in general. Indeed, it forms a barrier, the hydrolipidic film, which protects the scalp from external aggressions (dehydration, pollution, UV rays...). Sebum also ensures the hydration of the hair. In fact, once synthesised, it gradually flows along the hair fibres and coats them, thus ensuring their moisturisation. However, due to hormonal imbalance or an external cause, it can happen that the sebaceous glands undergo an imbalance and produce an excess of sebum: this is referred to as hyperseborrhoea.

This excess sebum on the scalp leads to several problems, some more serious than others. Initially, one might consider a social inconvenience. Indeed, hyperseborrhea gives hair a greasy and dirty appearance, and tends to flatten it. This unattractive aspect of the hair can be a source of insecurity for those affected. They then react by increasing their number of weekly shampoos. However, this is a misguided solution because, when washed too frequently, the scalp can feel attacked. In defence, the production of sebum by the sebaceous glands increases: this then creates a vicious cycle.

Furthermore, an accumulation of sebum on the scalp creates a favourable environment for bacterial colonisation and parasitic infestation. This can contribute to the appearance of dandruff, which are small dead cells ranging in colour from white to yellow. Indeed, studies have highlighted a link between the fungus Malassezia and the presence of dandruff. These yeasts possess lipase activity, meaning they hydrolyse the triglycerides in sebum and release unsaturated fatty acids. These are metabolites that cause abnormal differentiation of keratinocytes, leading to anomalies in the stratum corneum, such as parakeratosis and dandruff. Finally, some unsaturated fatty acids released by Malassezia produce prostaglandins, pro-inflammatory mediators that can cause scalp itching.