Title: Mammalian meat allergy (alpha-gal syndrome) following tick bites
Author: Dan Gingold, MD, MPH
Development of IgE antibodies to the oligosaccharide galactose-alpha-1-3-galactose (alpha-gal) appears to be responsible for an acquired allergy to non-primate mammalian meat (i.e., beef and pork) and derived products. Antigen in the salivary apparatus of certain ticks (gross!!) can sensitize an IgE-mediated response to alpha-gal which is present in mammalian meat.
Symptoms are similar to other IgE-mediated hypersensitivity reactions, and can cause a delayed-onset reaction with hives, GI upset, or anaphylaxis after ingestion of red meat. Treatment with standard anti-histamines and epinephrine is effective. Individuals with no prior history of meat sensitivity can develop the syndrome at any age, often after exposure to the outdoors in tick-endemic areas. Skin and blood allergy testing can confirm the diagnosis. Symptoms can persist for years, but can recede over time if not exposed to further tick bites.
In the US, the primary tick responsible is Lone Star Tick (Amblyomma americanum), found primarily in the Eastern, Southeastern, and Midwestern US. Other tick species in Europe, Australia, and Asia have been found to induce the syndrome as well. Interestingly, there is a cross-reactivity with the monoclonal antibody Cetuximab (used to treat colorectal and head and neck cancers), an allergic reaction to which can also induce similar alpha-gal meat sensitivity.
Having first been described in 2009, the syndrome often goes unrecognized; increased physician awareness can inform the evaluation, diagnosis, and education of patients presenting to the ED with undifferentiated allergic reaction.
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