Food-Specific and Component IgE Threshold Levels That Predict Food Allergy in People With Elevated Total Serum IgE Levels and Atopic Dermatitis

* INCLUSION CRITERIA: Individuals must meet all of the following criteria to be eligible for study participation: 1. Aged 3-21 years. 2. Currently enrolled on study 15-I-0162, "Natural History and Genetics of Food Allergy and Related Conditions." 3. Has a total serum IgE level \>= 900 kU/L at time of screening. 4. Has a history of AD based on self-report or physician assessment. 5. Willing to undergo an oral food challenge to both placebo and test food. 6. Willing to allow storage of blood samples for future use in medical research. 7. Willing to allow genetic testing to be conducted on blood samples. 8. Has a primary care physician or other physician who will manage all health conditions related or unrelated to the study objectives. 9. Be willing to discontinue omalizumab or dupilumab within 6 months of a food challenge,and antihistamines and oral steroids prior to a food challenge, as these drugs might interfere with the oral food challenge procedure. Use of topical steroids will be allowed 10. Able to provide informed consent. EXCLUSION CRITIERIA: Individuals meeting any of the following criteria will be excluded from study participation: 1. Pregnant. 2. Known genetic disorder that causes an elevation in total IgE level or one that could affect the severity of an anaphylactic response. 3. Known cardiac disease. 4. Current use of a beta-blocker. 5. Active eosinophilic gastrointestinal (GI) disorder including eosinophilic esophagitis, currently symptomatic, unless they are currently on treatment and have had a negative esophageal biopsy via endoscopy within at least the past 18 months, and/or unless the study food is already in the participants diets. 6. Any chronic medical condition requiring long-term use of oral steroids. 7. Current or recent (within previous 6 months) use of omalizumab or dupilumab. 8. Any condition that, in the opinion of the investigator, contraindicates participation in this study. Co-enrollment guidelines: Co-enrollment in other trials is restricted, other than enrollment on observational studies. Consideration for co-enrollment in trials evaluating the use of a licensed medication will require the approval of the principal investigator. Study staff should be notified of co-enrollment on any other protocol as it may require the approval of the principal investigator.