Editing Retinol (section)

===Skin===
Deficiencies in vitamin A have been linked to an increased susceptibility to skin infection and inflammation.<ref name="Roche2021">{{cite journal | vauthors = Roche FC, Harris-Tryon TA | title = Illuminating the Role of Vitamin A in Skin Innate Immunity and the Skin Microbiome: A Narrative Review | journal = Nutrients | volume = 13 | issue = 2 | page = 302 | date = January 2021 | pmid = 33494277 | pmc = 7909803 | doi = 10.3390/nu13020302 | doi-access = free }}</ref> Vitamin A appears to modulate the [[innate immune response]] and maintains homeostasis of [[epithelial tissues]] and mucosa through its metabolite, retinoic acid (RA). As part of the innate immune system, [[toll-like receptors]] in skin cells respond to pathogens and cell damage by inducing a pro-inflammatory immune response which includes increased RA production.<ref name="Roche2021"/> The epithelium of the skin encounters bacteria, fungi and viruses. Keratinocytes of the epidermal layer of the skin produce and secrete [[antimicrobial peptides]] (AMPs). Production of AMPs [[resistin]] and [[cathelicidin]], are promoted by RA.<ref name="Roche2021"/> Another way that vitamin A helps maintain a healthy skin and hair follicle [[microbiome]], especially on the face, is by reduction of [[sebum]] secretion, which is a nutrient source for bacteria.<ref name="Roche2021"/> Retinol has been the subject of clinical studies related to its ability to reduce the appearance of fine lines on the face and neck.<ref name="Kong 2015" /><ref>{{cite web |date=7 November 2016 |title=Vitamin A and Skin Health |url=https://lpi.oregonstate.edu/mic/health-disease/skin-health/vitamin-A |access-date=10 August 2023 |website=Linus Pauling Institute |language=en}}</ref>