The skin is the body's largest organ and the first line of defense against pathogens, so perhaps it should not be so surprising that improving the skin's barrier function reduces systemic inflammation.
A recent study found that when subjects applied a skin cream designed to improve barrier function (containing cholesterol, ceramides and free fatty acids) all over their body for 30 days they had reduced levels of three markers of inflammation in their blood (Il-1b, Il-6 and TNF alpha).
medicalxpress.com/news/2019...
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Another study found that consuming coffee polyphenols improved autonomic nervous system function and skin barrier function:
ncbi.nlm.nih.gov/pubmed/295...
{ Doesn't help me since coffee, even decaf, causes neurogenic bladder / lower urinary tract issues - but OTOH coffee really improves my boggle game }