This objective is designed to test the feasibility and effectiveness of using walnut OIT to desensitize subjects with other tree nut allergy(s). We expect to demonstrate the effectiveness of walnut OIT by showing that subjects on walnut OIT will have negative double-blind placebo-controlled food challenges (DBPCFC) to a second tree nut following completion of a ~38 week course of walnut OIT. We also expect that compared to placebo OIT, walnut OIT will induce significant decreases in: 1) wheal (swelling) size from a skin prick test to a second tree nut, 2) serum-specific IgE to a second tree nut, and 3) adverse effects with accidental tree nut ingestion and 4) an increase in tree nut specific IgG4.