Immunotoxicology (sometimes abbreviated as ITOX) is the study of the toxicity of foreign substances called xenobiotics and their effects on the immune system. Some toxic agents that are known to alter the immune system include: industrial chemicals, heavy metals, agrochemicals, pharmaceuticals, drugs, ultraviolet radiation, air pollutants and some biological materials. The effects of these immunotoxic substances have been shown to alter both the innate and adaptive parts of the immune system. Consequences of xenobiotics affect the organ initially in contact (often the lungs or skin). Some commonly seen problems that arise as a result of contact with immunotoxic substances are: immunosuppression, hypersensitivity, and autoimmunity. The toxin-induced immune dysfunction may also increase susceptibility to cancer. The study of immunotoxicology began in the 1970s. However, the idea that some substances have a negative effect on the immune system was not a novel concept as people have observed immune system alterations as a result of contact toxins since ancient Egypt. Immunotoxicology has become increasingly important when considering the safety and effectiveness of commercially sold products. In recent years, guidelines and laws have been created in the effort to regulate and minimize the use of immunotoxic substances in the production of agricultural products, drugs, and consumer products. One example of these regulations are FDA guidelines mandate that all drugs must be tested for toxicity to avoid negative interactions with the immune system, and in-depth investigations are required whenever a drug shows signs of affecting the immune system. Scientists use both in vivo and in vitro techniques when determining the immunotoxic effects of a substance. Immunotoxic agents can damage the immune system by destroying immune cells and changing signaling pathways. This has wide-reaching consequences in both the innate and adaptive immune systems. Changes in the adaptive immune system can be observed by measuring levels of cytokine production, modification of surface markers, activation, and cell differentiation. There are also changes in macrophages and monocyte activity indicating changes in the innate immune system. Immunosuppression Some common agents that have been shown to cause immunosuppression are corticosteroids, radiation, heavy metals, halogenated aromatic hydrocarbons, drugs, air pollutants and immunosuppressive drugs. These chemicals can result in mutations found in regulatory genes of the immune system, which alter the amount of critical cytokines produced and can cause insufficient immune responses when antigens are encountered. These agents have also been known to kill or damage immune cells and cells in the bone