Food Allergy Triggered by Tick Bites


Erin McGintee, MD
 
 
Tick-borne illnesses are increasing on Eastern Long Island. From Lyme disease to Rocky Mountain Spotted Fever, from erlichiosis to babesiosis, just about every resident of the Hamptons can share a story about an ailment they have experienced as the result of a tick bite. Now there is another adverse reaction to tick bites that can be added to the list: meat allergy.  

In February 2009, researchers at the University of Virginia identified this novel allergy to mammalian meat. Patients develop allergic reactions 3-6 hours after ingestion of mammalian meat, such as beef, pork, or lamb. Poultry, fish, and shellfish do not trigger allergic reactions in these patients. The responsible allergen for this reaction has been identified as galactose-α-1,3-galactose (nicknamed α-gal), which is a blood group carbohydrate (sugar) present in all non-primate mammals.  

The α-gal allergy differs from most other food allergies in several important ways. First, the allergy develops in response to a carbohydrate allergen, whereas the vast majority of other food allergies are in response to a protein. Second, the reaction is delayed by 3-6 hours. Most food allergies occur within minutes of food ingestion, and almost universally will occur within 2 hours.  Third, patients who develop this allergy have previously been able to tolerate meat without issue, while most other food allergies present early in life. These unexpected findings raised a question for researchers: What is triggering the development of this allergy?  

It is not yet known what predisposes some patients to develop the α-gal allergy. The Lonestar tick is an aggressive species, and in indigenous areas, tick bites are a frequent occurrence.  It is clear that α-gal allergy is more likely to develop in patients who have sustained multiple bites. In my experience, α-gal allergy is more commonly seen in patients with jobs or hobbies that increase their risk of tick exposure.  Patients with the allergy often spend time hiking or mountain biking, hunting, landscaping, or gardening.  Additionally, patients who develop the allergy tend to experience local reactions to Lonestar tick bites that persist for weeks or even longer.  

Patients with α-gal allergy can present with symptoms ranging from generalized hives, swelling, and itching, to anaphylaxis, which is a multi-system allergic reaction that, in severe cases, can lead to death.  Due to the fact that reactions to α-gal occur 3-6 hours after meat ingestion, the classic patient gives a history of awakening in the middle of the night with severe itching, redness, and hives over their entire body.  Patients with more severe episodes may also describe abdominal cramping, vomiting, diarrhea, wheezing, shortness of breath, or even loss of consciousness.   

The patients invariably give a history of ingesting mammalian meat several hours prior to the reaction.  Reactions do not necessarily occur each time a patient ingests meat.  Reactions are more likely to occur when a large quantity of meat is consumed.  Meats that are higher in fat are more likely to trigger a reaction than leaner cuts. Gelatin, which is usually derived from beef or pork, contains α-gal, and there have been cases of patients experiencing clinical symptoms after gelatin ingestion.  

There is some suspicion that certain blood types predispose a patient to develop the allergy, but research has not shown any correlation between a specific blood type and development of the allergy.  In my own case studies, I have identified two sets of first cousins with the allergy, and a father and daughter who both have allergy to α-gal.  This suggests that there could be some sort of genetic predisposition for development of the allergy.   Most of the α-gal cases reported in the medical literature came from southeastern states. However, the Lonestar tick has become ubiquitous on the East End of Long Island, and so it serves to follow that cases of α-gal allergy are on the rise.  To date, I have identified over 180 patients with this food allergy.  

The Hamptons are unique in that, while they are clearly becoming a hotspot for α-gal allergy, they are also a hotspot for tourists and visitors from all over the New York Tri-State area. For this reason, I would expect to see an increase in the incidence of α-gal allergy throughout the entire region. Any patient with a history of possible tick exposure, who is now experiencing unexplained allergic reactions, should seek out consultation with an experienced allergist.

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Erin McGintee, MD  



References: Commins SP, Satinover SM, Hosen J, et al. Delayed anaphylaxis, angioedema, or urticaria after consumption of red meat in patients with IgE antibodies specific for galactose-α-1,3-galactose. J Allergy Clin Immunol. 2009;123:426–33. Commins SP, James HR, Kelly LA, et al. The relevance of tick bites to the production of IgE antibodies to the mammalian oligosaccharide galactose-α-1,3-galactose.  J Allergy Clin Immunol. 2011; 127(5): 1286-93.    
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