Oral food challenge (OFC) is the gold standard clinical diagnostic method for food allergies. However, because an OFC often induces anaphylaxis and other risks, a safer method for patients is desirable. Although tests using specific IgE to crude extracts have a high degree of clinical sensitivity, they have low specificity, which in most cases results in low diagnostic efficiency. Specific IgE to some allergen components have been associated with symptoms. In the present study, components that are effective in the diagnosis have been elucidated using allergic patients diagnosed by OFC. Here, an overview of the allergen components of plant seeds and the components useful for diagnosis are described.