From my investigation, the majority of seborrheic dermatitis symptoms are caused by three main factors:
- Increased microbial activity
- Unstable barrier function
- Altered immune response
And how these factors tie together is as follows:
- Increased microbial activity results in increased free fatty acid release (from the sebum)
- Instability of the skin's natural barrier leads to excessive penetration of the released fatty acids
- Immune system issues cause improper response to penetrating fatty acids
More specifically, the main fatty acid responsible for the above processes appears to be oleic acid. And interestingly, even in individuals unaffected by seborrheic dermatitis, application of oleic acid results in similar skin symptoms.
As a result, finding ways to reduce microbial activity and improve barrier stability may result in a reduced amount of oleic free fatty acid present while also preventing it’s penetration deeper into the epidermis.