Background Some aspects of diagnostic elimination/challenge diets in food protein-induced allergic proctocolitis (FPIAP) are still poorly defined. Objective This study investigated the symptom spectrum, time required for resolution of each symptom, triggering foods, and risk factors for multiple food allergies (MFA) in FPIAP. Methods Infants referred with visible blood in stool were enrolled after etiologies other than FPIAP had been excluded. Laboratory evaluation, clinical features and elimination/challenge steps were performed prospectively during diagnostic management. Results Ninety-one out of 102 infants (53 boys) were diagnosed with FPIAP. Eleven children did not bleed during challenges. Visible blood in stool began before two months of age in 63.6% of the infants not diagnosed with FPIAP, compared to 18.9% of the patients with FPIAP (p=0.003). Offending foods were identified as cow’s milk (94.5%), egg (37.4%), beef (10.9%), wheat (5.5%), and nuts (3.3%). MFA was determined in 42.9% of patients. Multivariate logistic regression analysis identified atopic dermatitis (AD) (OR 2.98, 95% CI 1.18-7.55, p=0.021) and an eosinophil count ≥300 cells/μL (OR 2.72, 95% CI 1.09-6.80, p=0.032) as independent risk factors for MFA. Blood and mucus in stool disappeared in a median three days (IQR: 1-14.5 days) and 30 days (IQR: 8-75 days), respectively. Conclusions A tendency to transient bleeding occurs in infants who present with bloody stool before two months of age. A two-week duration of elimination for blood in stool is sufficient to reach a judgment of suspected foods for FPIAP. Mucus in stool is the last symptom to disappear. Concurrent AD suggests a high probability of MFA in FPIAP.
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