BACKGROUND: The prevalence of allergic diseases has been dramatically rising in the United States and other developed nations over recent decades. Growing evidence suggests a partial role for the microbiome in the development of these allergic diseases. Food protein-induced allergic proctocolitis (AP) (also referred to as cow’s milk protein intolerance or allergy) is among the earliest and most common food allergic diseases of infancy, yet its pathophysiology is not well understood. The currently accepted clinical practice is to restrict the diet until 12 months of age.

CASE REPORT: We present 4 cases of clinically diagnosed AP whose symptoms quickly and completely resolved with probiotic Lactobacillus rhamnosus GG (LGG) monotherapy. All 4 infants avoided any dietary restrictions. The range of time from probiotic initiation to symptom resolution was 7–28 days.

CONCLUSIONS: These cases suggest an important role for the infant intestinal microbiome in the development of gastrointestinal mucosal food allergies such as AP. Prospective investigation of the intestinal microbiome in infants with AP may further our understanding of this disease’s pathogenesis. The potential use of probiotic monotherapy in the treatment of AP also warrants further investigation.

Keywords: Lactobacillus rhamnosus, Food Hypersensitivity - therapy, Probiotics - therapeutic use, Proctocolitis - therapy