Acute urticaria is defined as evanescent wheals with a duration period of up to 6 weeks. Yet within acute urticaria, IgE-mediated urticaria lasts rarely more than 48 h, whereas longer duration periods are frequently unfruitful with respect to diagnostic work-up. We hypothesize the differences in immunologic features in immediate type urticaria versus prolonged acute urticaria within the model of Anisakis simplex (A. simplex) sensitization-associated urticaria. We included 57 patients with gastro-allergic Anisakiasis (GAA) and urticaria duration of less than 48 h and 17 patients with A. simplex sensitization-associated prolonged acute urticaria (PROL), defined as urticaria duration between 3 days and 6 weeks. As control group served 23 patients with A. simplex sensitization-associated chronic urticaria (CU+). We compared total IgE as well as specific IgE, IgG and IgG4 against A. simplex. Median total IgE was higher in GAA than in PROL or CU+ [442 (interquartile range, IQR 198–995) vs. 117 (68–261) or 251 (94–382) kU/l, respectively]. Median-specific IgE was higher in GAA than in PROL or CU+ [62 (IQR 24.1–99) vs. 12.3 (6–30.9) or 14.2 (6.2–44.9) kU/l, respectively]. The differences were statistically significant at P < 0.001 for GAA against PROL and at P < 0.003 for GAA against CU+. Also, specific IgG and IgG4 levels were higher in GAA than in PROL or CU+ at the same significance level. The levels of total IgE or specific immunoglobulin isotypes were not significantly different between PROL and CU+. In the model of A. simplex sensitization-associated urticaria, immediate-type urticaria in GAA is immunologically different from prolonged acute urticaria, which, in turn, shows features nearer to chronic urticaria than to gastro-allergic Anisakiasis. Thus, in an allergological evaluation of urticaria, we propose a possible benefit of a distinction of the duration period at 48 h, and not 6 weeks, when differentiating acute versus chronic urticaria.