Our GI tract is essentially one long tube extending from our mouth to our anus, and one of its main functions is sequestering the external environment (such as food and bacteria) from our bloodstream.When these defenses fail, it can lead to intestinal permeability and have a wide range of effects on our health, including our skin. This article will review the pathophysiology and causes of intestinal permeability as well as clinical methods to test for it. It will also review published research on the association between intestinal permeability and skin conditions such as eczema, psoriasis and dermatitis herpetiformis.