1 HOW THEY MAY START.
"The immune system is like the body's army — it spends the earliest years of your life distinguishing friends from enemies so it can protect you from invaders. Our culture has become so fastidious about hygiene, however, that doctors worry the immune system may not encounter many threats until adolescence or beyond, when it's more likely to make a mistake. It's not uncommon for an autoimmune attack on, say, your joints or thyroid to first happen or flare after an unrelated virus or infection. And an autoimmune attack can come seemingly out of nowhere, possibly due to a combination of genetics and the environment."