The purpose of this study is to evaluate the clinical usefulness of assessing specific human allergy antibodies and other immunologic parameters associated with the diagnosis, evolution, and management of allergic disease.

The purpose of this study is to strengthen our ability to understand the long-term effects of food immunotherapy on the immune system and how it may induce tolerance to foods that participants were once allergic to. Investigators hope to determine tools and immunologic parameters that can help predict sustained desensitization and tolerance to food allergens following food immunotherapy. By evaluating the in-depth characteristics of allergy antibody populations and other immunologic parameters and comparing them to clinical disease, the investigators may uncover a more sound way to diagnose, follow and treat food allergic disease over time. Investigators will follow up with participants who underwent immunotherapy to food allergens as volunteers in clinical trials at the Sean N. Parker Center and assess whether they experience sustained desensitization to these foods in the long-term. Investigators will investigate the properties of the participants' immune cells and how they are affected over time by the ingestion of these food allergens. Investigators will follow the significance of different dosing regimens in terms of achieving tolerance. Differences in immune cell characteristics and other biological parameters may help predict the nature of a participant's tolerance to the food allergens and may help in the development of tools to determine permanent tolerance.

Inclusion Criteria:

• Patients ages 6 months through 70 years who have previously undergone a food immunotherapy protocol only at our center.

Exclusion Criteria:

• None. However, if a participant becomes pregnant, their clinic visit may be postponed until after delivery and/or lactation period. These subject can postpone visits for one year and choose to skip visits during pregnancy and another year after (if breastfeeding).

Participants who underwent immunotherapy in clinical trial at the Sean N. Parker Center