Predictive factors for the persistence of cow's milk allergy.

Cow's milk allergy (CMA) is usually transient, but recent studies have shown a later acquisition of tolerance to CM. Our aims were to characterize a population of Portuguese children with CMA and to identify predictive factors for the persistence of this food allergy. Children with CMA observed in our Paediatric Allergy Clinic between 1997 and 2006 were selected. Demographic and clinical data were collected from medical records. The group of children who tolerated CM before the age of 2 was compared with the group of children who tolerated CM beyond that age or persisted with CMA until the end of the study. Multivariate logistic regression analysis was used to investigate independent predictive factors for the persistence of CMA beyond the age of 2. In the subgroup of children with IgE-mediated CMA, the acquisition of tolerance was analysed using Cox regression. In this population of 139 children, the majority presented more than one symptom (73%) affecting more than one organ (51%), with cutaneous (81%), gastrointestinal (55%), respiratory (16%) manifestations and/or anaphylaxis (3%). Thirty-two per cent developed asthma, 20% atopic eczema, 20% rhinoconjunctivitis and 19% other food allergies over time. The acquisition of tolerance was different in the whole population versus the subgroup with IgE-mediated CMA: 34%versus 0% at the age of 2, 55%versus 22% at the age of 5 and 68%versus 43% at the age of 10. Immediate allergic symptoms, asthma and other food allergies were independent factors for the persistence of CMA beyond the age of 2. Higher maximum weal diameter on skin prick test to CM and higher maximum level of specific IgE to CM were associated with reduced likelihood of acquiring tolerance in the subgroup of children with IgE-mediated CMA. In conclusion, children with IgE-mediated CMA acquire tolerance to CM at older age. Clinical parameters and allergy tests may be helpful in defining prognosis. CM-allergic children tend to develop other atopic conditions and need specialized follow-up in the long term.