Walnut Oral Immunotherapy for Tree Nut Allergy

Inclusion Criteria: * Age 6 to 45 years, either sex, any race, any ethnicity with a convincing clinical history of walnut or another tree nut allergy and either a positive prick skin test (\> 3mm) or serologic evidence of allergic sensitization (defined as specific IgE \> 0.35 kU/L) to walnut and at least one other tree nut. * A positive 2000 mg oral food challenge at enrollment to walnut and to one other tree nut. * Written informed consent from participant and/or parent/guardian * Written assent from all subjects as appropriate * All females of child bearing age must be using appropriate birth control Exclusion Criteria: * History of severe anaphylaxis to walnut or other tree nuts, defined as symptoms associated with hypoxia, hypotension or neurologic compromise (cyanosis or SpO2 \< 92% at any stage, hypotension, confusion, collapse, loss of consciousness; or incontinence). * Known allergy to oat * Chronic disease (other than asthma, atopic dermatitis, rhinitis) requiring therapy or other respiratory or medical conditions deemed by the investigator to put the subject at increased risk of anaphylaxis or poor outcomes from receiving OIT or undergoing food challenge. * Poor control or persistent activation of atopic dermatitis * Active eosinophilic or other inflammatory (e.g., celiac) gastrointestinal disease in the past 2 years. * Participation in any interventional study for food allergy in the past 6 months * Participant is on "build-up phase" of immunotherapy (i.e., has not reached maintenance dosing). * Severe asthma (2007 NHLBI Criteria Steps 5 or 6, see Appendix 2) or poorly controlled mild or moderate asthma * Inability to discontinue antihistamines for initial day escalation, skin testing or OFC * Use of omalizumab or other non-traditional forms of allergen immunotherapy (e.g., oral or sublingual) or immunomodulator therapy (not including corticosteroids) or biologic therapy within the past year * Use of beta-blockers (oral), angiotensin-converting enzyme (ACE) inhibitors, angiotensin-receptor blockers (ARB) or calcium channel blockers * Pregnancy or lactation