This protocol is designed to better characterize a sub-population of peanut sensitized individuals who may be non-allergic, despite significant sensitization, or who may be allergic, but at high threshold doses. By specifically targeting participants who met the initial screening criteria of the active adult PN OIT study, Protocol 2012p002153 / AADCRC MGH-004 (MGH-004), but failed to react during the pre-treatment 443 mg challenge to peanut, the investigators anticipate that the investigators will identify individuals who have become spontaneously tolerant, despite persistent sensitization. The investigators might also find that clinical sensitivity persists but only with higher thresholds, or that sensitivity has increased (or is variable) since the previous allergen exposure. By repeating DBPCFCs through to a full serving dose (7.4 gram), the investigators will distinguish participants who react only at higher doses from those who were not truly peanut allergic, address whether their sensitivity has changed, and have the opportunity to further investigate their immune response to peanut allergen.

The primary objective of the study is to identify and characterize a sub-population of high-threshold peanut allergic individuals and characterize their immunological phenotype in comparison with the low-threshold peanut allergic individuals enrolled in the adult PN OIT study (NCT01750879).

Clinical Objective:

To evaluate the clinical status of peanut-sensitized individuals previously passing a DBPCFC to 443 mg as being either: non-allergic, stably high-threshold allergic or more clinically reactive on repeat exposure.

Inclusion Criteria:

• Failure to react to 443 mg of peanut protein during the DBPCFC1 visit of protocol 2012p002153 / AADCRC MGH-004.
• Males and females of all ethnic/racial groups aged 7-55 years old who are otherwise healthy.
• Willingness to sign consent (or for parent/guardian to sign consent).
• Willingness to sign the assent form, if consent provided by parent/guardian.

Exclusion Criteria:

• History of severe anaphylaxis
• Severe or Moderate asthma
• Poorly controlled asthma
• Diagnosis of other severe or complicating medical problems, including autoimmune or chronic immune inflammatory conditions or gastrointestinal inflammatory conditions
• Inability to cooperate with and/or perform oral food challenge procedures
• Primary Immune Deficiency
• Current use of beta blockers, angiotensin converting enzyme inhibitors, or monoamine oxidase inhibitors
• Women of childbearing potential who are pregnant, planning to become pregnant, or breastfeeding
• Use within the past 6 months of other systemic immunomodulatory treatments
• Clinical signs or symptoms of anemia
• Hematocrit <0.36 for adult females or <0.38 for adult males
• Hematocrit <0.34 for children 7-18 years of age
• Weight <23 kg

A sub-population of peanut sensitized individuals who may be non-allergic, despite significant sensitization, or who may be allergic, but at high threshold doses.

A subset of patients screened for NCT01750879 but were not randomized due to threshold reactivity >300 mg peanut protein

4 weeks

Patient recall of adverse events, with emphasis on accidental ingestion reactions.