This is a short review of the literature with a bias toward the author's work. Small amounts of dietary antigens are taken up into the circulation. B-cell responses to foods (antibodies and antibody-secreting cells) occur as a physiological event locally and in the circulation in all three major immunoglobulin classes. A low levels of IgE is also a normal phenomenon. IgA anti-gliadin antibodies represent an exception. Antibody titers in general tend to decline with age. T-cell responses specific for foods are low in the circulation of healthy subjects. T-cell cytokines are more frequently produced in the gastrointestinal mucosa compared with the circulation. Results indicate that the phenomenon of oral tolerance takes place in humans. Oral tolerance within the T cell system may represent an important regulatory mechanism for normal immunity.