Despite improved health care, hygiene, and modern facilities, there is a global rise in autoimmune and metabolic disorders. Coinciding with this is the overall weakening of immunity and increase in allergic reactions. Food and nutrition play an essential role in developing, maintaining, and activating the immune system. Understanding how an individual's diet and nutritional status impact the immune system can unravel many opportunities and challenges. In this review, we discuss the immunomodulatory potential of nutritional and non-nutritional components of food. We will also delineate the mechanism by which diet and its ingredients affect the immune system's development and regulation. Besides, we will give a brief overview of food allergens and the mechanism by which they induce allergenicity. Finally, we will discuss immune-enhancing functional foods and the associated concerns. Food and nutrition is a significant determinant of immunity of an individual. Diet not only affects the development of immune system, but it also helps in the maintenance of immunity. • Dietary pattern is a significant factor underlying the increase in incidents of metabolic, allergic, and autoimmune diseases. • Nutrient and non-nutrient components in food play a crucial role in development, maintenance, and modulation of immune system. • Gut microbiome and epigenetic modulation are the important mechanisms for diet induced immunomodulation. • Bridging the gap between the popularised immunomodulatory functions of food and its scientific validation is urgently needed. [ABSTRACT FROM AUTHOR]