 Peanut allergy is known to cause severe anaphylactic reactions. Compared with other food allergies, it tends to be more persistent and its prevalence seems to be rising. Currently, there is no proven treatment other than strict avoidance. We are attempting to decrease the risk of anaphylaxis on accidental ingestion by desensitizing subjects to peanut using peanut mucosal immunotherapy PMIT. We are also studying the effect of PMIT on the peanut-specific immune response to determine if tolerance to peanut protein will develop. Based on our preliminary work and recent studies supporting the importance of early oral exposure in tolerance induction, we propose that early treatment of peanut allergy with PMIT will be safe and effective. Children ages 9 to 36 months with peanut allergy will be randomized to receive high or low dose PMIT using peanut flour. Peanut-allergic subjects receiving no intervention will serve as controls. Subjects will undergo desensitization on the first day and then increase the doses gradually to a maintenance dose. Doses will be taken daily at home except for dose increases which will be done on the research unit. Subjects will undergo a double-blinded, placebo-controlled food challenge DBPCFC if challenge criteria are met. Subjects passing the first challenge will stop PMIT and repeat the DBPCFC to assess tolerance. Outcome variables of interest include response to oral food challenges OFC, skin prick testing, peanut specific serum immunoglobin E IgE, immunoglobin G IgG, and immunoglobin G4 IgG4 and stool immunoglobin A IgA, T and B cell responses, quality of life, and adverse events. These longitudinal results will be compared between high and low dose PMIT groups and controls using appropriate statistical analysis. 