Inclusion Criteria:
* The subject is at least 18 years of age.
* The subject has a history of gastrointestinal alpha-gal allergy defined by elevated test for α-gal allergy (α-gal IgE \>0.1 U/L) due to complaints of either abdominal pain or discomfort, diarrhea, nausea with or without vomiting, or a combination of those complaints, within the last 5 years. The subjects must have experienced one or more of the four symptoms at least once monthly for at least two months. The subjects will fill out a symptom questionnaire of the presence of these four symptoms (abdominal pain or discomfort, diarrhea, nausea, vomiting), frequency and severity (mild, moderate, or severe) for the 3 months prior to diagnosis.
* The subject has experienced symptomatic improvement on a mammalian meat-free diet over at least a month's time, defined by saying "yes" to the following question: "On the alpha-gal avoidant diet, have you had adequate relief of gastrointestinal symptoms?"
* The subject has elevated α-gal IgE titer on screening for the trial if they do not have a positive titer within 6 months of enrollment.
* The subject is willing to not take nonsteroidal anti-inflammatory medications, leukotriene modifiers or steroids 14 days prior to challenge.
* The subject is willing to sign the informed consent form.
Exclusion Criteria:
* The subject has health conditions that would pose a significant threat in the face of anaphylaxis or treatment for anaphylaxis (e.g., cardiac disease, unstable angina pectoris, arrhythmias).
* The subject is allergic to mannitol.
* If female, the subject is pregnant.
* The subject has a history of chronic GI conditions, including inflammatory bowel disease, celiac disease, chronic pancreatitis with continued symptoms (experience moderate-severe abdominal pain, diarrhea, or nausea/vomiting that occur more frequently than once weekly)
* The subject has diarrhea (one or more loose stools that conform to the container), moderate to severe abdominal pain, or vomiting within 10 days prior to the challenge.
* The subject has a history of severe allergic reaction on mammalian meat ingestion (respiratory distress, chest pain or cardiopulmonary compromise)
* The subject is unwilling to receive intramuscular epinephrine.
* The subject is anticipated to use omalizumab within 6 months of enrollment.
* The subject is anticipated to use systemic steroids within 28 days of food challenge.
* The subject is anticipated to use leukotriene modifier within 14 days of food challenge.
* The subject is unable to not use nonsteroidal anti-inflammatory drugs for 14 days prior to challenge.
Additional Exclusion Criteria for Subjects Undergoing Transnasal Endoscopy and Biopsy
* Known conditions that are contraindications to transnasal endoscopy, or in the opinion of the investigator any condition that would interfere with the study objectives.
* History of head and neck malignancy or anatomical deformities of the nasopharynx
* Severe anxiety
