In a prospective study, 5 healthy dogs and 5 dogs with atopic dermatitis were included in the study. Samples collected from the these dogs served for total lipid and palmitoylethanolamide and related compounds (2-AG) quantification, morphometrical and densitometrical assessment of mast cells. The levels of all analysed NAEs and 2-AG were significantly elevated (p < 0.05). In particular PEA levels showed the highest increase, being more than 30-fold higher in atopic dermatitis lesional skin than in normal non-atopic skin.
The authors discussed this finding thus:
Opposite to the decrease of total lipid extracts, the levels of PEA and related lipid mediators (i.e., OEA and 2-AG) were shown here to increase in AD samples compared to healthy ones. Among all the analysed bioactive lipid compounds, PEA levels were more than 30-fold higher in AD lesional skin compared to normal non-atopic skin. Moreover, if one considers the total decrease of lipid content, the overall increase of PEA and the other examined lipid mediators is dramatic and once more might witness the role of NAEs and 2-AG in cellular homeostasis in the face of external stressors provoking, for example, inflammation. Currently, it is widely accepted that the endogenous formation of these bioactive lipid mediators plays a pro-homeostatic role, by being part of a protective response to cellular injury. In particular, PEA levels have been measured in mammalian skin and found to change in response to stressful conditions, both in animal models [51] and epidermal cell cultures. The increase in tissue levels of PEA is now considered an auto-protective mechanism, while the decrease is usually regarded as an exhaustion of the response.
The hypothesis is highly substantiated by the favourable effects of PEA administration: mice with contact dermatitis [50], hypersensitive Beagle dogs [54] and cats with eosinophilic granuloma all benefited from PEA treatment in terms of reduced allergic skin reactions.
