RichardFWhite

would this mean they have immune cells sensitive to high osmotic pressure?

The Wikipedia article doesn't really do the condition justice, since there are cases where people cannot drink water either, and none of the explanations in the Wiki article explain why people with this condition cannot drink plain water, but they can drink milk for example. Here is a severe case of the condition. Note that it is mentioned she drunk a mouthful of water by mistake, and then went into shock (that was treated with adrenaline). https://www.thefreelibrary.com/JUST+ONE+CUP+OF+WATER+COULD+KILL+LITTLE+HEIDI%3B+Girl's+deadly+allergy...-a061152595

I read some people have a bad immune reaction if they drink plain water (tap, distilled, sparkling water, etc) and I read about a girl who could not drink even a sip of plain water because it'd send her into anaphylaxis, but if they drink tea, milk or cola they have little to no reaction, so how would their immune cells 'know' if they just drunk plain water? The water molecules floating around in a glass of milk (>90% water) are still water molecules, right? Why would the water/liquid in the body be seen as ''OK'' but plain water is ''not okay'' in these people's immune system cells?