The Epithelial Barrier Theory is a comprehensive explanation for the global, epidemic-level rise in chronic health conditions over the past 65 years. The theory, postulated by Akdis, proposes that exposure to toxic substances introduced by industrialization and modern lifestyle changes disrupts the epithelial barrier of the skin, upper and lower airways, and gut mucosa and causes microbial dysbiosis triggering an inflammatory immune response that can initiate or aggravate many chronic inflammatory diseases.