Severe reactions from roe without concomitant fish allergy.

Background: Although fish allergy is common, no studies have been published on allergy to fish roe.

Objective: To describe 2 cases of IgE-mediated allergy to 2 roe species.

Methods: Two patients, one with local symptoms and the other with anaphylaxis following ingestion of roe, underwent skin prick testing (SPT) with 2 roe species, whitefish roe (WFR) and rainbow trout roe (RTR). Serum samples were taken for IgE measurement and immunoblotting to identify roe allergens. Inhibition studies were performed to scrutinize the cross-reactivity between the roes and to fish.

Results: The results of the SPTs with the roes were clearly positive in both patients but negative in control persons. The results of SPTs to all other foods were negative. Roe-specific IgE levels were elevated in the serum samples of both patients. Immunoblotting revealed different IgE-binding patterns of the extracts and different inhibition profiles with the serum samples. In WFR blotting, both serum samples detected a heavy IgE-binding band at approximately 20 kDa, which was not inhibited with fish. Cross-reactivity between the roes was demonstrated in the patient with local symptoms from RTR but not in the patient with anaphylaxis from WFR. The first serum sample also detected several IgE-binding bands in the RTR blot, the most intensive at 21 to 23 kDa and 30 kDa, which were partially inhibited by WFR and more completely with fish. The anaphylaxis patient did not detect allergens in the RTR blot. After the investigation, the patients have remained symptom free and able to consume all kinds of fish without problems.

Conclusions: IgE-mediated allergy to roe is possible without concomitant fish allergy. Roe allergy should be explored in patients who test negative to fish but are suspected of having seafood-related allergy.