After a mechanical skin injury, a web of chemical signals creates a vicious cycle that expands and activates the mast cells that cause allergic food reactions. In the skin, cells called keratinocytes produce IL-33, which travels through the blood to the small intestine where it activates innate lymphoid cells type 2 (ILC2s). The ILC2s, also known as effector cells, release IL-4, which signals mast cells to expand, as well as IL-13, which stimulates tuft cells in the intestinal lining (via IL-13). In a synergistic feedback loop, the tuft cells stimulate the ILC2s (via IL-25), reinforcing the signal to expand and activate mast cells. When stimulated by food antigens, the mast cells release mediators that make the intestine more permeable, releasing food antigens into the blood.