D1.267 - Clinical Features and Dairy Triggers for Cow’s Milk Allergy among 342 Chinese Children in a University-affiliated Allergy Clinic in Hong Kong

Cow's milk (CM) is one of the nine major food allergens. Acknowledging the latest EAACI diagnostic algorithm which suggests patients with strong clinical history and CM sensitization obviates the need for double-blind placebo-controlled food challenge (DBPCFC), we adopted this pathway for our "confirmed milk-allergic (CMA)" subgroup. This study compared the features between Hong Kong children with and without CM allergy.

A 26-year, single-center, retrospective study was conducted on children aged <18 years with suspected CM allergy. Those with allergic reactions (urticaria, angioedema or anaphylaxis) within 2 hours of CM contact or ingestion were classified as "probably CM-allergic" (PMA), with the remaining deemed "unlikely CM-allergic" (UMA); CM allergy (CMA) was defined by PMA with positive CM-specific skin prick test (SPT; ≥3 mm) or CM-specific IgE (sIgE; ≥0.35 kU/L). Preceding CM triggers were categorized by 4-step milk ladder with increasing allergenicity. Statistical analyses were performed by GraphPad Prism, with statistical significance set at 0.05.

342 patients were included for analysis (PMA: n=98, CMA: n=86). The age at first clinic visit for CMA subgroup (median 1.8 years, interquartile range [IQR] 1.1-3.6 years) was younger than that of PMA-not-CMA subgroup (median 3.0 years, IQR 1.4-5.9 years) (P=0.004) but comparable to the UMA group (median 2.4 years, IQR 1.2-5.1 years). SPT results of CMA group was larger than those of the UMA and PMA-not-CMA groups (P≤0.0001), yet intragroup (CMA patients overall versus with anaphylaxis versus without anaphylaxis) results were insignificant. Fresh CM and dairy products, corresponding to Step 4 of milk ladder, were the most common triggers for all CMA, PMA-not-CMA and UMA subgroups. Food triggers from temporal analysis revealed increasing numbers of overall parent-reported, probable and confirmed CM allergy cases from 2000-2004 to 2020-2024. A key limitation is the lack of DBPCFCs to ascertain CM-allergic status for UMA patients with vague history.

Chinese children with CMA are significantly younger at their first clinic visit, and have larger SPT wheal diameters when compared to PMA-not-CMA and UMA patients. Most CM-allergic children react to dairy products at Step 4 of milk ladder. This single-centre retrospective study observes an increasing trend for CMA cases from 2000 to 2024 in Hong Kong. (partly funded by Hong Kong Institute of Allergy research grant)