Causes of seborrheic dermatitis

Is your skin covered in small red patches, often on the face or scalp? Are these patches thick, a little greasy and come off easily when scratched? This is known as seborrheic dermatitis, a condition that affects around 3% of adults ⁽¹⁾.
This condition can appear from birth, during puberty, or later in adulthood.
So what's the cause? Seborrheic dermatitis, causes and aggravating factors: a closer look at current knowledge.

3 factors identified as the cause of seborrheic dermatitis

Seborrheic dermatitis, which causes redness and flaking, is caused by a number of factors. This is what is known as a “ multifactorial ” condition. Although the exact mechanisms are not yet fully understood, three main elements are currently recognised:

• excessive production of sebum in areas rich in sebaceous glands ⁽¹⁾.
• the abnormal proliferation of a yeast of the genus Malassezia, which is naturally present on the surface of the skin and makes up the skin’s microbiome;.
• inflammation of the skin, causing redness and flaking of the face or scalp.

Research continues to progress on the subject of seborrheic dermatitis’ causes, revealing that other factors could also play a role, such as a weakened immune system or a dysfunction of the skin barrier due to changes in the composition of ceramides (essential lipids present in the skin) ^(2). 

Hormonal factors

Seborrheic dermatitis may be linked to a hormonal imbalance, particularly of androgen hormones, also known as male hormones (present in men but also in women in small quantities). When they are in excess, these hormones strongly stimulate the sebaceous glands, modifying the composition of lipids in the sebum and creating an environment conducive to the proliferation of Malassezia yeast⁽³⁾.

Environmental factors

High humidity ⁽⁴⁾ or low temperatures are linked to the development of seborrheic dermatitis. On the other hand, UV light tends to reduce its development by reducing the growth of Malassezia yeasts^(5). 

Stress and lifestyle

Many people have observed the link between seborrheic dermatitis and causes of stress, fatigue or overwork, linked to lifestyle ⁽⁶⁾. A vicious circle can set in, as the visible manifestations of the condition also generate and perpetuate stress. 

Factors that aggravate seborrheic dermatitis

Several aggravating factors are known:

• External factors
  • The climate: damp, cold. 
  • Sweat.
  • Alcohol and tobacco consumption. 
  • Stress. 
  • Diet is also thought to play a role in the development of lesions⁽²⁾. 
• Internal factors 
  • Genetic predisposition. 
  • Hormonal disorders can influence sebum secretion and disrupt the immune system. 

Seborrheic dermatitis and other conditions

Seborrheic dermatitis is generally an isolated skin condition. However, it can appear in certain specific contexts:

• in immunocompromised people (very weakened immune system) such as HIV or COVID-19 patients ⁽³⁾. 
• in people with Parkinson's disease: the reduction in dopamine leads to a disturbance in the production and composition of sebum. 
• certain psychiatric conditions are also thought to be favourable for the development of seborrheic dermatitis.

In terms of treatment, the doctor may suggest:

• a targeted treatment to regulate sebum production and limit Malassezia yeast growth and reduce inflammation. 
• an appropriate skincare routine. 
• personalised support to help manage the triggers identified, such as stress management techniques, nutritional advice, help with quitting smoking, etc.