FCER1A and anaphylaxis: More importantly, CSU FMT, but not HC FMT, significantly increased passive cutaneous anaphylaxis (PCA) responses in recipient mice, with markedly increased vascular permeability (+70%, P < 0.0001, Fig. 2b) and MC degranulation (+240%, P < 0.0001, Fig. 2c), as well as significantly increased rates of MCs (CD45+CD117+FcεRIα+ cells)39 in skin tissue detected by FACS (P < 0.001, Fig. 2d).