PURPOSE Recent studies have used the term "gastroallergic anisakiasis" to describe incidental gastrointestinal infection with Anisakis spp. larvae, proposed as a causative agent of food hypersensitivity. However, it is unknown whether this condition represents an independent disease entity distinguishable from acute gastric anisakiasis. To better understand the role of the allergic response in Anisakis infections we examined the clinical and immunological implications of Anisakis-specific IgE. METHODS A prospective study was performed in a geographic region where the consumption of raw seafood is common. Case subjects who had been clinically diagnosed with gastroallergic anisakiasis were selected, along with controls who frequently ate raw seafood but had never experienced gastroallergic anisakiasis-like symptoms. Clinical and immunological features were compared based on atopic status, sensitization rates to Anisakis, and serum titer of Anisakis-specific IgE. RESULTS Seventeen case subjects and 135 controls were included in this study. The case subjects had experienced gastrointestinal symptoms after raw seafood ingestion, along with additional mucocutaneous, respiratory, or multisystemic symptoms. Case subjects were significantly sensitized to Anisakis excretory-secretory product and crude extract compared with controls (76.5% vs 19.3%, P<0.001, and 88.2% vs 30.3%, P<0.001, respectively). Anisakis-specific serum IgE titers were also significantly higher in case subjects than in controls. Both the results of skin prick tests and elevated Anisakis-specific IgE titers (>17.5 kU/L) were found to be reliable indicators for the diagnosis of gastroallergic anisakiasis. CONCLUSIONS Among patients presenting acute gastric anisakiasis-like symptoms, a diagnosis of gastroallergic anisakiasis may be strongly supported by a high Anisakis-specific IgE titer.