Another component of the skin's natural defence mechanism are various antimicrobial peptides. The most famous and well documented for these are cathelicidin, dermcidin and b-defensins. Lack of these peptides has been attributed to the progression of various skin diseases (source). These peptides are produced from amino acids which must be obtained through diet, and their expression appears to depend on various environment factors. For example, one study showed that simply watching a humorous video increased the production of dermcidin-derived peptides (source).
Though the internal production of these antimicrobial peptides may be hard to predict and control, researches have been attempting to mimic their functions using peptides produced in the lab with promising results (source). However, there do not appear to be any products currently on the market which utilize antimicrobial peptides for the treatment of seborrheic dermatitis.
In the meantime, it may make sense if we attempt to improve our natural levels of these antimicrobial peptides. This topic is discussed in more detail in the in Skindrone Approach section of this book.