Natural History and Genetics of Food Allergy and Related Conditions

* GENERAL INCLUSION CRITERIA: All participants must meet the following criteria: 1. Be 2 to 99 years-old at the time of enrollment for participants who will be seen at the NIH CC; be 0 (newborn) to 99 years-old at the time of enrollment for participants who will submit mail-in samples or participate in telehealth visits. Only viable neonates will be enrolled. 2. Willing to allow storage of blood, buccal swabs, saliva, nasal swabs, stool samples, and other clinically appropriate tissue specimens for future use in medical research 3. Required to have a primary care or other physician who will manage all health conditions related or unrelated to the study objectives ADDITIONAL INCLUSION CRITERIA FOR AFFECTED PARTICIPANTS In addition to the general criteria listed above, affected participants must meet 1 of the following criteria: 1. Have a clinical history of an immediate hypersensitivity reaction to food(s) and be sensitized to food allergen(s) (as evidenced by positive SPT or allergen-specific IgE testing) 2. Be sensitized (as evidenced by positive SPT or allergen-specific IgE testing) to food allergen(s) but have no overt clinical history of IgE-mediated symptoms when they eat that food(s) 3. Have a suspected genetic or congenital disorder potentially associated with food allergy or related condition, as determined by the principal investigator (PI) or associate investigators (AIs) 4. Have a diagnosis of eosinophilic esophagitis (EoE), or clinical suspicion for EoE as determined by the principal investigator (PI) or associate investigators (AIs) 5. Have a history of atopic dermatitis based on self-report or physician assessment. ADDITIONAL INCLUSION CRITERIA FOR UNAFFECTED RELATIVES: In addition to the general criteria listed above, unaffected relatives must meet the following criteria: 1. Be a relative of an affected participant 2. Be unaffected by food allergy (as determined by clinical history and/or allergy testing) or be unaffected by the genetic condition under study ADDITIONAL INCLUSION CRITERIA FOR HEALTHY VOLUNTEERS In addition to the general criteria listed above, healthy volunteers must meet the following criteria: 1. Be unrelated to an affected participant 2. Be unaffected by food allergy (as determined by clinical history and/or allergy testing) or be unaffected by the genetic condition under study ADDITIONAL PROCEDURE- SPECIFIC INCLUSION CRITERIA: The following additional inclusion criteria apply for participants undergoing leukapheresis: 1. Age \>= 18 years 2. Stable hematologic parameters (definition: white blood cell count \> 2,500/microL, hemoglobin \> 10 g/dL, and platelet count \> 75,000/microL) GENERAL EXCLUSION CRITERIA: Participants will be excluded for any of the following: * Presence of conditions that, in the judgment of the investigator or the referring physician, may put the participant at undue risk or make them unsuitable for participation in the study. * Inability to participate for the duration of the study. * The PI deems that participation in the study would not be expected to advance the study goals. ADDITIONAL PROCEDURE- SPECIFIC EXCLUSION CRITERIA Additional exclusion criteria apply for unaffected relatives and healthy volunteers who are undergoing endoscopy with biopsies for research purposes. Unaffected relatives and healthy volunteers will be excluded from participating in this procedure if they meet any of the following criteria: 1. uncontrolled asthma or Grade 3 or higher by the American Society of Anesthesiologist s Physical Status Classification System (https://journals.lww.com/anesthesiologyopen/fulltext/2026/04000/american\_society\_of\_anesthesiologists\_statement\_on.2.aspx) 2. history of adverse reaction to conscious sedation or general anesthesia required for endoscopy 3. hemoglobin \< 11 g/dL 4. platelet count \< 100,000 microL 5. PT INR \>1.3 or PTT prolonged by \> 3 seconds 6. pregnant or breastfeeding 7. viral screens positive for HIV or hepatitis B or C 8. severe unstable myocardial ischemia or cardiomyopathy 9. severe hypoxemia due to chronic pulmonary disease 10. recent abdominal surgery 11. anticoagulant therapy that cannot be interrupted 12. history of reflux disease within the last 3 years or use of acid-suppression medication (including over-the-counter medications such as Tums, Rolaids, Zantac, Prilosec OTC, or Prevacid OTC) within the last 2 months 13. chronic GI or immunologic disease 14. clinically indicated EGD or colonoscopy within the past 12 months 15. use of systemic or inhaled corticosteroids within the past 4 months 16. have a history of EGID including EoE 17. younger than 18 years of age