Cow's milk allergy (CMA) has different clinical presentations according to age. The study aimed to evaluate the extent of CMA as a cause of pediatric constipation and determine the appropriate timing of tolerance to cow milk in such patients. The study included 60 patients suffering from chronic functional constipation, 27 of whom did not respond to 2 month laxative therapy (group I). Thirty age and sex matched apparently healthy infants and children were studied as a control group (group II). Serum specific IgE to cow milk proteins was measured. Withdrawal of cow milk and dairy products for a 1 month period was then followed by cow milk re-challenge over 2 wk. Patients were classified into: responders to this schedule (cow milk allergic=group Ia; n=21) and non-responders (non-cow milk allergic=group Ib; n=6). Eighteen CMA patients continued the study where nine of them underwent milk reinstitution after 6 months and another nine patients after 12 months of elimination. The frequency of CMA among constipated patients was 77.7%. Mean values of serum specific IgE to whole cow milk protein and beta-lactoglobulins were significantly higher in constipated patients (0.82+/-0.08, 0.79+/-0.13 IU/ml, respectively) compared with controls (0.26+/-0.14, 0.27+/-0.14 IU/ml, respectively) and in group Ia (0.99+/-0.08, 0.95+/-0.14 IU/ml, respectively) compared with group Ib (0.39+/-0.06, 0.37+/-0.10 IU/ml, respectively). Serum specific IgE was positive in 85.7% of CMA group, predominantly in class 2. Tolerance to cow milk was achieved after 6 months in only 22.2% compared with 88.8% after 12 months of elimination. In conclusion, CMA is shown to be a significant etiologic factor for constipation in infants and young children. Serum levels of IgE to cow milk proteins are helpful although not definitive for diagnosis. Based on this limited study, tolerance is better achieved after 12 months of strict cow's milk elimination.

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