Relationship between red meat allergy and sensitization to gelatin and galactose-α-1,3-galactose

Background: We have observed patients clinically allergic to red meat and meat-derived gelatin. Objective: We describe a prospective evaluation of the clinical significance of gelatin sensitization, the predictive value of a positive test result, and an examination of the relationship between allergic reactions to red meat and sensitization to gelatin and galactose-α-1,3- galactose (α-Gal). Methods: Adult patients evaluated in the 1997-2011 period for suspected allergy/anaphylaxis to medication, insect venom, or food were skin tested with gelatin colloid. In vitro (ImmunoCAP) testing was undertaken where possible. Results: Positive gelatin test results were observed in 40 of 1335 subjects: 30 of 40 patients with red meat allergy (12 also clinically allergic to gelatin), 2 of 2 patients with gelatin colloid-induced anaphylaxis, 4 of 172 patients with idiopathic anaphylaxis (all responded to intravenous gelatin challenge of 0.02-0.4 g), and 4 of 368 patients with drug allergy. Test results were negative in all patients with venom allergy (n = 241), nonmeat food allergy (n = 222), and miscellaneous disorders (n = 290). ImmunoCAP results were positive to α-Gal in 20 of 24 patients with meat allergy and in 20 of 22 patients with positive gelatin skin test results. The results of gelatin skin testing and anti-α-Gal IgE measurements were strongly correlated (r = 0.46, P <.01). α-Gal was detected in bovine gelatin colloids at concentrations of approximately 0.44 to 0.52 μg/g gelatin by means of inhibition RIA. Conclusion: Most patients allergic to red meat were sensitized to gelatin, and a subset was clinically allergic to both. The detection of α-Gal in gelatin and correlation between the results of α-Gal and gelatin testing raise the possibility that α-Gal IgE might be the target of reactivity to gelatin. The pathogenic relationship between tick bites and sensitization to red meat, α-Gal, and gelatin (with or without clinical reactivity) remains uncertain.