Cow's milk allergy in adults is rare but severe: both casein and whey proteins are involved

Background Studies on cow's milk allergy (CMA) in adults are scarce. Little is known about the clinical symptoms, eliciting doses (ED), and allergens involved. Objective The aim of this study was to analyse the clinical symptoms, ED and allergen recognition in adult CMA patients, compared with cow's milk (CM)-sensitized, but tolerant controls. Methods Adult CMA patients were evaluated by standardized questionnaires (n=30), skin prick tests (SPTs) and specific IgE for CM allergens (n=18), and a double-blind placebo-controlled food challenge (DBPCFC, n=10). A control group (n=25) of CM-sensitized, but tolerant adults was included. Results The majority of CMA patients (20/30, 67%) reported severe symptoms. In all patients participating in DBPCFC, CMA was confirmed. ED for subjective symptoms (0.3-300 mg CM protein) were significantly lower than that for objective symptoms (300-9000 mg CM protein). The severity of CMA by history and ED was not correlated with SPT or IgE. Patients had higher SPT reactivity than controls for CM, alpha-lactalbumin and beta-lactoglobulin (P=0.002, P=0.014 and P=0.004) but not for casein. Specific IgE to CM tended to be higher (P=0.068) and IgE to casein was higher in patients than that in controls (P=0.016). No difference was observed for IgE to alpha-lactalbumin and beta-lactoglobulin. Conclusion Adult CMA is severe in nature. ED are low, starting from 0.3 mg CM protein. Patients with CMA recognize the same major allergens (casein and whey proteins) as controls, but display a stronger SPT and IgE reactivity.