FCER1A encodes the high-affinity immunoglobulin E receptor α-subunit (FcεRIα), a critical cell surface receptor mediating IgE-dependent immune responses. Upon IgE binding and antigen cross-linking, FcεRIα initiates signaling cascades in mast cells, basophils, and eosinophils that trigger degranulation and secretion of vasoactive mediators, lipid mediators, and cytokines 1. This response provides host defense against helminth parasites and pathogenic threats, but dysregulation causes harmful allergic and anaphylactic reactions 2. Transcriptionally, PU.1, GATA1, and GATA2 transactivate the FCER1A promoter to regulate receptor expression on mast cells 1. Genetic variants in FCER1A associate with allergic disease susceptibility and serum IgE levels; notably, FCER1A polymorphisms interact with TLR2 variants to influence atopic dermatitis severity 3. FCER1A expression is elevated in atopic dermatitis lesions within inflammatory dendritic cell populations 4 and serves as a biomarker for non-response to anti-TNF therapy in inflammatory bowel disease 5. Genome-wide association studies identified FCER1A among loci influencing urticaria susceptibility through effects on mast cell biology 2. Notably, inhaled corticosteroids downregulate FCER1A expression in healthy airways, suggesting homeostatic type-2 signaling in respiratory mucosa 6.