Sometimes it's in the doc's head. I once had a pediatrician go on and on about how my son would need tubes in his ears because of some fluid that dripped out when I laid him on the examining table. I patiently listened to him until he was finished and then politely pointed out that the fluid was a bit of breast milk that had dripped down my son's cheek because he's a bit of a sloppy eater.
My doc has finally gotten frustrated with the recurring debilitating blistering rashes I have had for two years now. I asked, "could it be something autoimmune?", but she just answered, "you just have very sensitive skin".