Diagnosis of food protein-induced allergic proctocolitis (FPIAP) in infants is based on successive elimination and challenge diets with the suspected triggering food. However, certain facets of dietary management are still inadequately defined, especially among children with multiple food allergies (MFA).

In most infants, removal of the offending protein, most often cow’s milk, from the diet results in the resolution of rectal bleeding within 72 to 96 hours. For infants whose symptoms do not resolve within that period, however, the clinician needs to know how long the elimination diet should be applied, and how extensive it should be, to identify infants with MFA or those with no food allergy. Additionally, some infants whose rectal bleeding wanes with an elimination diet do not re-bleed while on a challenge diet.

Cow’s Milk & Egg Are Top Food Allergy Offenders

To gain better insight into the diagnostic elimination/challenge diets in FPIAP, my colleagues and I examined the symptom range, time required for resolution of each symptom, triggering foods, and risk factors for MFA in FPIAP, which was published in The Journal of Allergy and Clinical Immunology: In Practice. Infants with visible blood in the stool were included in our prospective, cross-sectional study after etiologies other than FPIAP had been eliminated. Laboratory evaluation, clinical features, and elimination/challenge steps were conducted prospectively during diagnostic management.

Our study team observed that 91 out of 102 infants with visible blood in the stool were diagnosed with FPIAP. Offending foods included cow’s milk (94.5%), egg (37.4%), beef (10.9%), wheat (5.5%), and nuts (3.3%), and MFA was established in 42.9% of patients. The two most frequent offending foods recorded in the same individual (among patients with MFA) included cow’s milk and egg (32.9%); egg was found in only three patients as a single offending food (Table).

We found that visible blood in stool cleared with a median time of 3 days with the diagnostic elimination diet. Resolution of visible blood in stool happened within 15 days in 86% of patients, within 3 days in 55%, and within 1 day in 38%.

Atopic Dermatitis a Risk Factor for MFA

We also observed that atopic dermatitis (AD) and an absolute eosinophil count of at least 300 cells/µL were found to be risk factors for MFA.

Our study provides clinicians with data that impact the current diagnostic elimination approach in two ways. In patients with no risk for MFA, a linear order of elimination can be adopted, step-by-step, according to the frequency of offending foods. In patients with a risk for MFA, elimination may be started with the two most likely offending foods, cow’s milk and egg.

Further Evaluation and Subsequent Studies Are Recommended

Because mucus in stool is one of the frequent symptoms of FPIAP, clinicians may sometimes over-diagnose FPIAP in infants without blood in stool, or else may overextend elimination diets based on the presence of mucus. Our prospective follow-up of the presence of mucus in stool showed that the condition improved in a median 30 days and was the last symptom to resolve. Disappearance of mucus was observed after the onset of complementary feeding in 64.8% of patients. This finding supports the concept that the elimination diet should not be prolonged based on the presence of mucus itself in cases for which blood has already receded.

We observed that cow’s milk and egg are the most common foods found together in patients with FPIAP, and that AD is a widespread allergic comorbidity and risk factor for MFA in patients with FPIAP. There is also a high probability that moderate-to-severe AD will exhibit IgE-mediated reactions. Therefore, it may be a prudent strategy for clinicians to simultaneously eliminate cow’s milk and egg as a first step in the diagnostic elimination diet in the presence of AD in patients with FPIAP. My colleagues and I would like to see these issues further evaluated in subsequent studies.