We have maybe a slightly different issue with alters and illness. If we "need" to be sick for some reason, real physical symptoms appropriate to that condition show up in the body. The response is much milder and of shorter duration than it used to be but it's still here. Even if the symptoms are manufactured, they feel real to us hosts.
The whole topic is extremely embarrassing because some of our most humiliating memories (still) involve this phenomenon playing out. Come to think of it, it seems an unavoidable conclusion that an alter, known or unknown, is behind this.
I can see how this would have been important in our childhood. Our DID mother would be our reliably sweet, nurturing mother (an alter) for long stretches only when we became ill or were seriously injured -- even though some alters tortured or tried to kill us, go figure. Remembering this detail before I realized that either of us had DID, I often wondered why I didn't turn into a total hypochondriac, since I sort of felt "rewarded" for getting sick.
We strongly suspect a different relative of having
Munchausen syndrome by proxy.