To assess the accuracy of skin prick tests (SPT)s with extract, diluted, and whole milk to detect desensitization in children with milk allergy undergoing oral immunotherapy (OIT).
Children with milk allergy were recruited at the Montreal Children’s Hospital and consenting participants were blindly randomized to have OIT. Children in the active arm received weekly increases in doses until 300 mL of milk was ingested daily. Paired t-test was used to compare SPT wheal diameter (vs negative control with glycerin) for milk extract (Omega), diluted 2% milk (1:10), and undiluted milk at study entry and when challenge with 300 mL was tolerated. SPTs for controls were conducted at study entry and 1 year later.
Among 21 children undergoing OIT, median age was 14.0 years (IQR, 12.0, 17.0) and 52.4% were males. The differences in wheal size from baseline to 300 mL were 5.3mm (95%CI, 3.7, 6.9) for milk extract, 4.5mm (95%CI, 2.1, 6.8) for diluted milk, and 6.2mm (95%CI, 3.2, 9.2) for whole milk (attained after an average of 8.9 months). Average SPT at desensitization was negative only for milk extract at 300 mL (<3.0mm).
Changes in clinical reactivity to milk during OIT are associated with substantial decrease in SPT size assessed by diluted, undiluted or by milk extract.