Red Meat Allergies After Lone Star Tick (Amblyomma americanum) Bites

James H. Diaz, MD, DrPH


South Med J. 2020;113(6):267-274. 

In This Article


Recent Investigations in the Mechanisms, Diagnosis, and Management of the α-gal Syndrome and Meat Allergies in Children and Adults

Historically, red meat allergies were rare, confined to atopic children, but they increased in prevalence following worldwide reports of the α-gal syndrome after tick bites. New investigations have begun to unravel the cellular mechanisms by which tick bites cause the α-gal syndrome, to differentiate the clinical presentations of the α-gal syndrome in children versus adults, and to recommend new patient-centered management strategies.[33–35]

In 2019, Chandrasekhar et al reported the results of their murine model study designed to identify the cellular mechanisms by which cutaneous exposures to tick bites induced the development of IgE antibody-mediated reactions to α-gal in meats.[35] The investigators subcutaneously administered A americanum antigens to mice and demonstrated that tick sensitization to α-gal followed by challenge with oral meat induced the production of IgE-specific anti-α-gal antibodies via T-lymphocyte-related reactions. In addition, the investigators identified CD4+ T cells and MyD88 signaling pathways as important underlying mechanisms for the induction of IgE responses to cutaneous tick antigen exposures in their in vivo murine model.

In a 2019 observational study of 261 children and adults (age range 5–82 years) with meat allergies, Wilson et al confirmed elevated α-gal-specific IgE antibody levels (≥0.35 IU/mL) in 245 subjects, most of whom (81%) became symptomatic in ≥2 hours after eating red meat.[33] Further component testing of study subjects stratified diagnoses as primary beef allergy in 1.1%, the pork-cat syndrome in 1.9%, and the α-gal syndrome in 95%. The levels of α-gal-specific IgE and the severity of allergic reactions were similar among subjects with and without traditional atopy in children (n = 35) and adults (n = 226). As anticipated, the α-gal-sensitized subjects tended to have nonblood group B.[15,33] The investigators concluded that the α-gal syndrome was significantly more common than food allergy, displayed a characteristic but not constant prolonged delay in symptom onset in children and adults, and could develop any time in life, even in nonatopic individuals.[34]

In 2020, Platts-Mills et al challenged the therapeutic dictum that all α-gal-sensitized patients avoid all mammalian meat and dairy products.[35] The investigators recommended that all patients with the α-gal syndrome be evaluated initially for their specific sources of sensitization, such as by gelatin, bioprosthetic heart valves, mammalian-derived plasma expanders or pancreatic enzymes, or animal dander because only a minority of patients could benefit from avoiding a wide range of food products prepared with mammalian constituents.

Prevention of Tick Bites

Personal protective measures to prevent tick bites include wearing appropriate clothing, using insect repellant, and performing regular tick checks of the body. Wearing long pants tucked into socks, shoes not sandals, long-sleeved shirts, and light-colored clothing can aid in keeping ticks off the skin and in making them easier to spot on clothing. Impregnating clothing with permethrin is a highly effective repellant against ticks and other insects. The topical application of insect repellants containing 20% to 50% N,N-diethyl-meta-toluamide (more commonly known as DEET) or 7% to 20% picaridin is another effective and recommended measure. Ticks should be removed in contiguity with their mouthparts with forceps, tweezers, or specially designed tick-removal devices, and not by squashing ticks with fingers, which could create infectious aerosols or transmit pathogens across dermal barriers (Figure 3).

Figure 3.

The proper techniques to remove embedded ticks include identifying the skin-embedded tick without dislodging it; grasping the tick with tweezers, forceps, or other tick-removal device across the thorax; exerting a removal force straight upward and perpendicular to the skin to avoid splitting off the mouthparts that inject the salivary gland antigens and pathogens; and washing the tick bite site with soap and water. Illustration from the Centers for Disease Control and Prevention.