The skin is our bodies largest organ. It forms an essential barrier between our bodies and the external environment. Lipids are a critical component of the skins healthy function protection and are essential to its stability .
Two of the most essential functions that lipids have in the skin are:
- Maintenance of barrier permeability – regulating the movement of water and electrolytes
- Antimicrobial barrier – protection against toxic microbes and pathogens
Without adequate lipids present in the stratum corneum (top most layer of the skin) our bodies would have issues in maintaining a normal fluid balance, alterations in serum electrolytes, and both local and systemic infections would become more common .
Essential Fatty Acid Metabolism and the Skin
We obtain the majority of our lipids from diet. However, the lipids our bodies obtain from food, are not yet in the state which our cells can utilize them. First, our bodies need to break down the more complex lipids (triglyerides) into much more basic lipids (single fatty acids and monoglycerides). And only once broken down, they can be transported throughout the body and utilized by our cells.
Linoleic acid (omega 6 fatty acid) and its derivatives play a critical role in the structure and function of the natural skin barrier [3, 4]. Accordingly, researches have long speculated that a variety of common skin issues may be the result of an inadequate lipid availability in stratum corneum.
A significant body of work from the 1930s to 1950s suggested that a deficit in omega 6 essential fatty acids can lead to a variety of inflammatory skin conditions . But as the research on the subject progressed, it became apparent that these conditions may not actually be the result of a deficit. Instead, new findings reveled that the issue may simply be related to abnormalities in the metabolism of these fatty acids [6, 7, 8].
More specifically, the research indicated that defective delta-6-desaturase function may be at the core of atopic eczema .
What is delta-6-desaturase
Delta-6-desaturase is an enzyme which the body uses to convert several essential fatty acids. Most prominent of it’s functions includes the conversion of LA (linolenic acid) to GLA (gamma-linolenic acid).
Essential Fatty Acid Metabolism and Seborrheic Dermatitis
Most of the research on essential fatty acids examined adults and children affected by atopic eczema. Research in the case of seborrheic dermatitis is much more sparse. Nonetheless some clues do exist.
A 1991 study showed a striking difference in the blood level of essential fatty acids in individuals affected by seborrheic dermatitis when compared to health individuals. In this paper, the researchers concluded that since levels of linolenic acid were generally normal, the overall difference is likely related to defects in the metabolism of these fats .
Another study from 1993 examined seborrheic dermatitis in 30 children (1-6 months of age) with infantile seborrheic dermatitis. The results of this study also suggested a diminished delta-6-desaturase activity may be at the core of skin symptoms .
In addition to these studies there are a few more clues which indicate potential issues in this area. More specifically, in seborrheic dermatitis affected individuals the following abnormalities were documented:
- Lower concentrations of unsaturated acids in the skin surface lipids, possibly due to a metabolic impairment 
- Lower squalene content, raised cholesterol content and a calculations suggested the total unsaturated fatty acids were lowered 
Though these studies didn’t necessarily examine delta-6-desaturase activity, they did show abnormalities in unsaturated fatty acid levels. As a s result, it does seem that metabolic deficiencies may play a substantial role in seborrheic dermatitis progress.
Possible issues in sebum composition as a whole
The second study mentioned above noted alterations in the metabolism of sebum as a whole and not just the unsaturated fatty acids.
This section made the connection between seborrheic dermatitis and potential issues in metabolism of lipids. These are some of the key takeaways:
- Lipids are an essential component of healthy skin function and are an integral part of its natural defense barrier
- Researchers have long suspected skin lipid abnormalities may be at the core of some of the most common skin issues
- Some of the most important fatty acids in the skin barrier function are omega 6 fatty acids and their derivatives
- Deficiency of an enzyme responsible for the conversion of omega 6 fatty acids plays an important role in the progression of atopic eczema
- Skin lipid abnormalities have also been documented in seborrheic dermatitis, but no specific pathology has yet been established
- Current studies suggest that low levels of unsaturated fatty acids and deficiencies of conversion enzymes may be integral