SummaryWe propose a new oral immunotherapy (OIT) method that includes a small amount of a food allergen in the diet. However, it is not clear whether this method will induce oral desensitization and immune tolerance. Therefore, we investigated the therapeutic effectiveness using a 1% food allergen diet in an allergic mouse model. C3H/HeJ mice were sensitized to ovomucoid (OM) in alum four times at 12-d intervals. Sensitized mice were divided into two groups: the OIT group (19% casein diet with 1% OM) and the non-treated group (20% casein diet without OM). The non-sensitized mice served as the non-allergy group. The OIT treatment was performed for 4 wk. To assess desensitization and immune tolerance, we performed oral and intraperitoneal OM challenges, assessed vascular permeability of the dorsal skin, and measured allergic biomarkers. The OIT group exhibited significantly lower oral symptom scores and vascular permeability than the non-treated group, but the two groups did not differ in intraperitoneal allergy symptom scores. Furthermore, the OIT group had significantly higher OM-specific IgA levels in their plasma than the non-treated group. However, the plasma levels of OM-specific IgE, IgG1, and IgG2a were not significantly different between the OIT and the non-treated groups. These results suggest that the proposed OIT using an OM-supplemented diet may induce desensitization, but not immune tolerance, in an OM allergic mouse model. Key Words oral immunotherapy, ovomucoid, food allergy, diet Globally, 240-550 million people may suffer from food allergies (1). Recently, the prevalence of food allergies has increased by 18% among children under 18 y of age (2, 3). Dietary avoidance of specific allergens is recommended as the first-line approach in the management of food allergy (4). In Japan, egg allergy is the most prevalent food hypersensitivity among the pediatric population, exceeding cow's milk allergy (4). A major cause of egg allergy is ovomucoid (OM), which constitutes approximately 11% of egg white protein (5, 6). Oral immunotherapy (OIT) is a new treatment for food allergies (4, 7). This treatment involves inducing desensitization through continuous food-allergen intake. However, according to the Japanese pediatric guidelines for food-allergy treatment, OIT is not often recommended because of the risk of inducing the allergic symptoms during the treatment (4). Moreover, current data are inadequate to establish proper OIT protocols, such as allergen dose and timing, need for escalation, therapy duration, and routes of administration.There are some reports of the OIT protocol in an allergic mouse model (8)(9)(10)(11)(12). We propose a new OIT regimen that involves mixing a small amount of allergen powder in the diet. Some merits of this OIT method are: 1) the allergen dose is divided, 2) allergen doses ingested can be easily adjusted, and 3) the taste and smell of the allergen is masked. Few reports exist regarding the relationship between oral desensitization and an allergencontaining diet in allergic ...