Intervention Arm – Multi Nut OFC
A multi-tree nut butter recipe was developed by the study dietitian that contains almond, cashew, hazelnut and walnut providing 1gram of each nut protein in a 20-gram (4 teaspoon) food challenge. This will be administered over 6 graded doses at 15-minute intervals (smear, 1/8tsp, 1/4tsp, ½ tsp, 1 tsp, reminder of 4 teaspoon dose).
The nuts selected were the most common tree nuts eaten in Australia and a 1g top dose of each nut protein was considered representative of nut ingestion in a toddler diet.
The nut butter was trialled as part of the pilot study (n=20) and was found to be palatable and taken well by participants. The pilot study nut butter was prepared by the study dietitian but for the current trial it will be manufactured offsite by a food manufacturing company (Royal Nut CompanyR) who prepare commercially available nut butter products. The nut butter is prepared on machinery that does not manufacture peanut containing products and tested to ensure it was free of peanut protein.
Primary Outcome- IgE-mediated tree nut allergy at 18 months of age.
The algorithm for classifying tree nut allergy at 18 months is outlined below and in figure 1:
  1. Definite tree nut allergy- has evidence of tree nut sensitization (SPT≥3mm) and either a positive OFC or parental report of a reaction consistent with IgE-mediated food allergy to an individual tree nut via the home introduction protocol
  2. Probable tree nut allergy – Based on review by study clinician panel. Participants will be referred to review panel if there is: 1) evidence of tree nut sensitization (SPT≥3mm) AND 2) OFC result is missing (declined by parent) AND 3) has either a history of reaction that is unclear or reports a late reaction after the OFC has ceased.
  3. Tree nut tolerant- has a negative individual tree nut OFC or successfully tolerated the tree nut via home introduction (ingested 1 teaspoon on >3 occasions).
  4. Probable tree nut tolerance – not sensitised (SPT <3mm) but no known ingestion or negative multi-nut OFC and no further tree nut ingestion.
  5. Inconclusive –sensitised (SPT≥3mm) but ingestion has not occurred, and participant declines OFC.
Figure 1. Algorithm for determining Tree Nut Allergy at 18 months