Imagine for a minute that you have the flu. There are millions of little viruses in your body, all smaller than anything you can imagine. Your immune system systematically finds and wipes them out. It can locate a single virus or organism in your body and irradicate it. Now, think about this by logical extension: you are turning the most powerful part of your body on your own tissues, intentionally. Even if you don't feel it happening, you are causing terrible amounts of damage and not allowing them to heal.
My uncle has MS. He has been in a wheel-chair for the past 30 years, from a single MS event. He got tired while at work, sat down, and never stood up again. His immune system did that to him, without pain or warning. Auto-immune diseases are not something to screw with. We have people on here with the celiac cancer, people with failing kidneys, people who lost all their hair.
One of my coworkers was a Celiac who cheated from time to time. He was 45 and looked 65. I say was, because he died last year. This stuff can kill you.