Is it rusting? If so, heat it, scour it, and re-season it.
Is the seasoning flaking off? Again, heat, scour, and re-season.
I always wash my CI by hand, dry on the heat, then rub with some shortening while it's still hot.
I don't have an automatic dishwasher right now, but if I did, and someone put one of my CI pans through it, I'd go nuts. But then, if someone put ANY of my pans through a dishwasher, I'd go nuts, because I always wash all my pans by hand.
Peace, Love, and Vegetable Rights!
Eat Meat and Save the Plants!