Mammalian meat allergy, often referred to as alpha gal allergy, is a recently discovered and increasingly prevalent condition with a wide range of clinical manifestations resulting from an allergic reaction mediated by IgE antibodies directed against galactose-alpha-1,3-galactose. Patients can frequently experience nausea, diarrhea, indigestion, urticaria, angioedema or anaphylaxis typically arising three to six hours after ingestion of mammalian protein. Interestingly, patients have longstanding tolerance to mammalian meats years before symptom onset and were bitten by the lone star tick, Amblyomma americanum, prior to symptom onset. We present a case of mammalian meat allergy diagnosed after the discovery of a tick on a patient’s lower extremity during a colonoscopy.
A 64-year-old female with a history of IBS-D presented to our clinic several years of chronic urticaria, diarrhea, nausea and abdominal pain, typically occurring after food intake. An extensive workup of chronic diarrhea was largely unrevealing. However, during a colonoscopy a tick was discovered on the patient’s inner thigh and was removed. Given her symptom complex, additional blood work was pursued and revealed elevated levels of serum alpha gal IgE. Further history revealed multiple prior tick bites with severe localized skin reactions in the past. At a follow-up visit after avoidance of mammalian meat and byproducts, the patient reported a 90% improvement in her symptoms, with just one formed bowel movement per day. She continued to have some bloating and abdominal pressure, but overall her symptoms were drastically improved with a modified diet.
This case illustrates the challenges in identifying alpha gal allergy, a unique and frequently misdiagnosed allergic condition that is increasing in prevalence. The clinical presentation of alpha gal is unique when compared to other food allergies as there are a lack of immediate oral symptoms and episodes only occur after lone star tick exposure. Additionally, onset of symptoms occurs three to six hours after mammalian meat consumption, making its association difficult to uncover. The case also highlights the importance of taking a thorough history, with higher suspicion in patients with recurrent episodes of urticaria, angioedema, gastroenteritis, or anaphylaxis without an obvious cause. Thus, improved awareness of alpha gal allergy is essential, particularly for providers located in endemic areas like the southeastern United States.