Autoimmune disease occurs because of autoimmunity -- an unnatural condition where the immune response, which normally protects the body from foreign invaders and substances backfires and attacks normal tissues. Antibodies and white cells are directed against parts of the body, causing inflammation and injury to certain tissues and organs. The triggers are usually unknown. There are over 40 such diseases including juvenile diabetes, multiple sclerosis, rheumatoid arthritis, myasthenia gravis and lupus.
Autoimmune disorders occur almost exclusively in developed countries. People in poor nations without modern amenities like running water, flush toilets, washing machines, and sterile backyards don’t usually get these diseases; neither do those who grew up on a farm with lots of animals.. It is posited that playing in the dirt, being dirty, and being exposed to bugs and infections trains your immune system to recognize what is foreign and what is “you.”
In the USA, autoimmune diseases, when taken all together, are a huge health burden affecting an estimated 24 million people in 2016. They are the eighth leading cause of death among women, shortening the average patient’s lifespan by eight years. The annual health care cost for autoimmune diseases is $120 billion a year representing nearly twice the economic health care burden of cancer (about $70 billion a year).