The role of intestinal dysbiosis is becoming clearer

The link between the digestive tract and atopic dermatitis has been studied for many years, and new ground has been broken thanks to studies on the intestinal flora made possible with bacterial metagenomic techniques. Through the detailed analysis of the fecal microbiome of atopic and non atopic subjects, Korean researchers have found no major difference in the diversity patterns of the species present. However, they have identified an abnormality, a dysbiosis, in the subspecies Faecalibacterium prausnitzii, primary bacterium in the digestive microbiota. From early childhood, L26 species are more preponderant in atopic subjects than A2-165 species. This dysbiosis leads to a decrease in the production of butyrate and propionate, short chain fatty acids with anti-inflammatory properties. The resulting inflammation increases intestinal permeability and the absorption of poorly digested foods, toxins and bacteria, leading to a TH2 immune system imbalance resulting in atopic manifestations. The next step will consist in investigating if modifications in intestinal flora, and in particular the proportion of Faecalibacterium prausnitzii subspecies, are likely to prevent or improve atopy. In 1921, Otto Prausnitz, after whom the bacterium was named, observed circulating antibodies as a result of the immediate allergy caused by the sub-cutaneous injection of serum from his colleague Küstner, who was allergic to fish. Prausnitz then ate some fish and developed an urticarial plaque around the injection site.