There has been a significant increase in the incidence of allergic diseases for several decades. There is even a talk of “an epidemic of the 21^st century” in relation to, for example, food allergies (FAs). Modern lifestyle and environmental factors contribute to a further increase in disease incidence. The authors proved that the first three years of life are a very important period for the proper development of microflora and taking actions in the context of prevention/therapy; and antibiotic therapy and diet play a significant role in shaping a stable microbiota. An adverse immune reaction to food is referred to as a FA. Immune reactions to food allergens can generally be divided into: IgE-mediated, non-IgE-mediated and mixed. Reactive oxygen species (ROS) are involved in the pathogenesis of FAs. Oxidative stress induces inflammation in tissues; excessive amounts of ROS damage intestinal tissue, disrupt normal cell function, and in eosinophilic esophagitis (EoE) impair the Keap1/Nrf2 pathway.