J-M Leyva-Castillo et al have found evidence suggesting the skin-gut communication, which explains a link between food allergy and atopic dermatitis. Researchers demonstrated that scratching the skin could trigger a series of immune responses culminating in an increased number of activated mast cells involved in allergic reactions in the small intestine. Scientists found that on scratching the skin, some cells respond by stimulating the production of cell-signalling protein interleukin-33 (IL-33) which enters the blood. IL-33, on reaching the gut, combines with IL-25, a protein secreted by cells in the lining of the intestine. This activates type 2 innate lymphoid cells (ILC2s), which in turn triggers the production of cell-signalling proteins IL-13 and IL-4, responsible for the expansion of intestinal mast cells. The expansion of mast cells makes the intestinal lining become more permeable to allergens entering the tissue. The study was performed on the mouse by inducing scratching by tape stripping the skin. Researchers found that the mice which underwent tape stripping showed more severe reactions to food allergen compared to normal mice. Scratching may thus instigate food anaphylaxis in atopic dermatitis by expanding and activating intestinal mast cells.
Source: Immunity 23 April 2019 DOI:https://doi.org/10.1016/j.immuni.2019.03.023 https://www.cell.com/immunity/fulltext/S1074-7613(19)30140-2