The immune system is the system of specialized cells and organs that protect an organism from outside biological influences using several strategies, of which early activation of defense is one of the most important. As their name implies, immunomodulators weaken or modulate the activity of the immune system, thereby decreasing the inflammatory response. Natural immunomodulators act to strengthen weak immune systems and to moderate immune systems that are overactive. Plant sterols and sterolins, aloe vera, and ginseng root are examples of natural immunomodulators. Both natural and synthetic immunomodulators are most often used in organ transplantation to prevent rejection of the new organ, and in autoimmune diseases such as rheumatoid arthritis. Since the late 1960s, they have also been used to treat people with inflammatory bowel disease (IBD).Interestingly, during the late 1800s and early 1900s, many medical practitioners began to recognize infections as serious complications of opiate addiction. Experimental evidence demonstrates the detrimental effects of opiates on immunity in humans and animals. While opiates directly modulate host immunity, their effects on physiological function of nonspecific host mechanisms are thought to also alter immune responses and play an important role in increased susceptibility to infection.