The overproduction of sebum, or hyperseborrhea, also affects the scalp. This multifactorial phenomenon leads to itching and the appearance of dandruff. Learn more about this physiological process and discover some tips for restoring a healthy scalp.
Scalp: What is hyperseborrhea?
What is scalp 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.
What are the causes of hyperseborrhea of the hair?
Hyperserborrhoea is a multifactorial issue. However, the primary cause of this scalp imbalance is an excessive production ofandrogen hormones. The main androgen in men is testosterone, and in women, it is Δ-4-androstenedione and dehydroepiandrosterone. Within the sebocyte, these androgens are transformed by various enzymes into testosterone. This testosterone then reacts under the action of an enzyme, 5-α-reductase, to transform into dihydrotestosterone (DHT) which stimulates the activity of the sebaceous glands. Therefore, individuals whose 5-α-reductase is highly active, due to genetic reasons, are more prone to hyperserborrhoea.
Another cause of hyperseborrhea is the increase in external aggressions on the scalp. Pollution, UV rays, unsuitable hair products... all these factors lead to an over-stimulation of the sebaceous glands and the production of an excess of sebum to protect the scalp. Age also plays a role in hyperseborrhea. Indeed, under hormonal influence, the sebaceous glands are active from the first month of life. Their activity then increases during puberty before slowly decreasing from adulthood. It drops dramatically for women after menopause. Thus, although it is not systematic, people under 40 are often more affected by hyperseborrhea.
Finally, there is a connection between diet and hyperseborrhea. Indeed, frequent consumption of high glycemic index foods, such as white bread, chips or certain biscuits, generates a spike in blood insulin levels. This increase in insulin levels also triggers a rise in androgen levels and thus indirectly leads to excessive sebum secretion.
Note : There are several ways to limit hyperseborrhea at the level of the scalp, such as adopting purifying treatments like our purifying shampoo or our purifying scalp treatment, protecting your hair, avoiding handling it excessively, maintaining a healthy and balanced diet...
BEYLOT G. Les cheveux gras. Actualités pharmaceutiques (2013).
WIKRAMANAYAKE T. & al. Seborrheic Dermatitis and Dandruff: A Comprehensive Review. Journal of clinical and investigative dermatology (2015).