KIT (CD117), a receptor tyrosine kinase that is the primary receptor for stem cell factor (SCF). KIT is critically expressed on mast cells, interstitial cells of Cajal, melanocytes, and hematopoietic stem cells. The SCF/KIT axis is essential for mast cell survival, proliferation, differentiation, and activation. In allergic and inflammatory diseases, mast cells are key effector cells that, upon activation, degranulate and release a plethora of pre-formed (e.g., histamine, tryptase) and newly synthesized mediators (e.g., leukotrienes, cytokines), causing immediate hypersensitivity reactions, itch, and tissue inflammation.