My previously healthy 25 year old patient is admitted because of an anaphylactic reaction 4 hours after having a hamburger. Could it really have been the hamburger?

Absolutely! It could be related to alpha-gal (galactose-alpha-1, 3-galactose) allergy (AGA), a condition found in thousands of Americans1.  AGA (also known as red meat or mammalian allergy) is a novel form of IgE-mediated anaphylaxis that typically occurs 3-6 hrs (not immediately) after ingestion of mammalian meat (beef, pork, lamb, bison, goat, vension); turkey, chicken, and fish do not contain alpha-gal1,2 . Another unique feature of AGA is that it seems to develop in adult life3.

What’s even more fascinating about AGA is its presumed causal relationship with prior bites of Amblyomma americanum (the lone star tick)4,5, found in many southern, midwestern and eastern states in the US (Figure).    The proposed mechanism of sensitization is that tick saliva contains alpha-gal (possibly from feeding on deer or other mammals), which causes production of IgE to this oligosaccharide5.  When mammalian meat (in our patient, a hamburger) is ingested by the sensitized individual, an anaphylactic  reaction may ensue.  The delay in reaction is thought to be due to the time it takes for alpha-gal to be absorbed from the gut4

The story doesn’t end here! Some medications contain alpha-gal due to inert ingredients such as gelatin or magnesium stearate of bovine sources. At least one report of anaphylaxis in a patient with AGA has been blamed on medications with bovine-derived magnesium stearate6.  Measles-mumps-rubella and zoster vaccines may also contain alpha-gal, with zoster vaccine implicated in a case of anaphylaxis. 7

 Currently,  the FDA does not require manufacturers to disseminate this information, so when  in doubt, individual drug manufacturers should be contacted. 



Figure: Lone start tick and its distribution in USA (Courtesy of CDC).

Updated Nov 11, 2019.

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  1. Van Nunen S. Galactose-alpha-1, 3-galactose, mammalian meat and anaphylaxis:a world-wide phenomenon? Curr Treat Options Allergy 2014;1:262-77.
  2. Kar I, Gong M, Muglia C, et al. Alpha-gal (mammalian meat) allergy: implications for pharmacists. Pharmacy Times, May 27, 2015.
  3. Commins SP, Platts-Mills TAE. Anaphylaxis syndromes related to a new mammalian cross-reactive carbohydrate determinant. J Allergy Clin Immunol 2009;124:652-57.
  4. Commins SP, Platts-Mills TA. Delayed anaphylaxis to red meat in patients with IgE specific for galactose alpha-1, 3-galactose (alpha-gal). Curr Allergy Asthma Res 2013;13:72-77.
  5. Steinke JW, Platts-Mills TAE, Commins SP. The alpha gal story: lessons learned from connecting the dots. J Allergy Clin Immunol 2015;135:589-97. This is a must read for anyone interested in the subject!
  6. Muglia C, Kar I, Gong M, et al. Anaphylaxis to medications containing meat byproducts in an alpha-gal sensitized individual. J Allergy Clin Immunol Pract 2015; 3: 796-97.
  7. Stone CA, Hemler JA, Commins SP, et al. Anaphylaxis after zoster vaccine:implicating alpha-gal allergy as a possible mechanism. J All Clin Immunol 2016;139 (5). DOI:10.1016/j.jaci.2016.10.037


Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Massachusetts General Hospital, Harvard Catalyst, Harvard University, its affiliate academic healthcare centers, or its contributors. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!

My previously healthy 25 year old patient is admitted because of an anaphylactic reaction 4 hours after having a hamburger. Could it really have been the hamburger?

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