Skin Prick Testing
Nine peanut-allergic subjects and three non-allergic healthy controls aged 19 to 29 years old were recruited to the Montreal Children’s Hospital for Skin Prick Testing (SPT) after obtaining informed consent. Subjects were considered allergic based on previous history suggestive of immediate allergy to peanut and the presence of previous positive SPT to peanut (wheal diameter greater than 7 mm), detection of serum-specific IgE to peanut proteins (>0.35 kU/L) and/or a positive oral food challenge to peanut.
Peanuts processed by roasting, autoclaving, roasting then autoclaving, and autoclaving then roasting, along with raw peanuts, were further processed into protein extracts as described above. Extracts of each condition were diluted to equal concentrations equivalent to the commercial standard peanut extract (Allergy Canada Limited, Thornhill, ON, LOT No: 3467710) as measured by Bradford Assay. The SPTs were conducted by placing a drop of each extract, as well as the standard commercial extract, on the forearm and making a small scratch on the arm using a solid bore needle. Saline diluent and Histamine (1mg/mL, ALK-Abello Pharm., Inc., ON, Canada) were used as negative and positive controls, respectively. After 10 minutes, the size of the wheal diameter was measured (in mm). All skin tests were performed by an experienced allergy nurse. Research Ethics Board (REB) approval was obtained from the McGill University Health Centre (MUHC-REB 2020-5745).