Immunotoxicology (sometimes abbreviated as ITOX) is the study of immune dysfunction resulting from exposure of an organism to a xenobiotic. The immune dysfunction may take the form of immunosuppression or alternatively, allergy, autoimmunity or any number of inflammatory-based diseases or pathologies. Because the immune system, plays a critical role in host resistance to disease as well as in normal homeostasis of an organism, identificantion of immunotoxic risk is significant in the protection of human, animal and wildlife health.

In the non-adult (embryo, fetus, neonate, juvenile, adolescent) this study is referred to as Developmental Immunotoxicology (commonly abbreviated as DIT). For most toxicants examined to date, the developing immune system exhibits a heightened sensitivity compared with that of an adult. For this reason, DIT screening has applications to human, animal and wildlife health protection.