not-yet-known not-yet-known not-yet-known unknown Characteristics of Fish Allergic Subjects: Self-reported History and sIgE Distribution A total of 200 physician-diagnosed fish-allergic subjects were recruited (median age 5.0 years, range 0.8 – 33 years), who had an early onset of fish allergy at a median of 9 months (3-60 months). Using a sIgE cut-off at 0.35 kUA/L, 166 subjects were sensitized to at least one of the nine fish extract ImmunoCAP tests that were tested, while 34 subjects were negative to all sIgE tests including fish parvalbumins rGad c 1 and rCyp c 1. The sensitized subjects had significantly higher total IgE and SPT wheal diameters when compared to non-sensitized ones (Table 1). Freshwater fishes were found to be a more frequent cause of IgE-mediated reaction among the 166 sensitized subjects, by which 98 (59%) reported allergic reactions to freshwater fishes while only 8 (5%) reported tolerance. Meanwhile for 130 subjects who had eaten marine fishes, a remarkably higher proportion of subjects (n=56, 43.1%) reported tolerance (Fig 1A). Grass carp was the most consumed freshwater fish in our population (79 subjects had a consumption history), and only 6 subjects (7.6%) reported tolerance. Salmon and tuna were the most frequently tolerated marine fishes (45/102 [44.1%] for salmon, 14/27 [51.9%] for tuna). Grouper was the least tolerated marine fish with only 6/58 (10.3%) subjects reported its tolerance. Among the sensitized subjects, more than half (98/166, 59%) were positive to all 11 ImmunoCAP tests (multi-sensitized), 64/166 were oligo-sensitized (sensitized to multiple fishes but not all the nine fishes) while 4/166 were mono-sensitized. The proportion of patients tolerating freshwater fishes and grouper remained low in multi-, oligo- and mono-sensitized subjects (Fig 1B & C). The distribution of tolerance patterns was more obvious in oligo- and mono-sensitized subjects, by which the proportion of individuals tolerating marine fishes and salmon exceeded those with reported allergy (52.5% and 60.4% tolerance, respectively). Subjects multi-sensitized to all 11 ImmunoCAP tests (n=98) were less likely to tolerate any one fish when compared to other subjects (n=68) (p<0.0001; OR: 4.66). Among the sensitized subjects, >90% of subjects were sensitized to tilapia, grass carp or catfish with high sIgE titer (median 4.8-5.9 kUA/L) by ImmunoCAP (Table 2). In contrast, tuna and halibut were the least allergenic with only 67.5% and 72.2% of subjects being IgE positive, respectively. sIgE levels to these latter fishes were also significantly lower (0.7 kUA/L and 1.4 kUA/L, p<.0001). When dissecting the sIgE class distribution (Table 2 & Fig 1D), the percentage of patients with negative sIgE (class 0) remarkably decreased from 32.5% to 4.2% along the fish ladder of tuna, halibut, salmon, cod, herring, grouper, catfish, grass carp and tilapia. However, catfish, grass carp, and tilapia, compared to only around 10% to fishes like cod, salmon, and halibut, or even down to 5.4% to tuna (Table 2 & Fig 1D). The four mono-sensitized subjects were sensitized only to salmon or tuna, and they were all non-reactive against the two parvalbumins rCyp c 1 (common carp) and rGad c 1 (cod) on ImmunoCAP. The median ratios of rCyp c 1/grass carp sIgE and rGad c 1/cod sIgE were 1.23 (range 0.04-9.83) and 2.45 (0-148) respectively. On the other hand, sIgE against tilapia, grass carp, catfish, grouper, herring and cod strongly correlated with sIgE against the two parvalbumins rCyp c 1 and rGad c 1 (r > 0.90) (Table 2), but only moderately correlated with halibut (r = 0.82 & 0.85), salmon (r = 0.76 & 0.77) and tuna (r = 0.71). Comparison of sIgE levels (reactivities) indicated that there are no statistical differences in sIgE between (1) tuna, halibut and salmon; (2) cod, herring and grouper; (3) catfish, grass carp and tilapia; and (4) halibut, salmon and cod (Fig 1E). Yet, herring-sIgE was statistically higher than both halibut-sIgE and salmon-sIgE, while catfish-sIgE was also statistically higher than both herring- and grouper-sIgE. For instance, sIgE against tilapia was on average twice as high as grouper and herring in our population, and more than 4-fold higher against halibut and salmon. The most significant difference was observed between tilapia and tuna, by which tilapia-sIgE was on average 11-fold higher than tuna-sIgE, and in some individuals, the sIgE titer differed by 70-fold. Correlation analysis indicated a significant positive correlation between sIgE level and incident of self-reported allergic reactions to the respective fish (r = 0.81, p = .0151) but not with the frequency of consumption to individual specific fish (r = -0.21, p = .6112) (Fig 1F &G).