Would a person live long if the mast cells somehow trained to fire upon exposure to H2O molecules? This woman says she cannot even drink a sip of water without needing an Epi-pen injected into her yet in her pictures she is not hooked up to a bed being IV'd adrenaline and looks quite alive.

They wouldn't live long enough to say anything.

They are mainly water (all people are) so those cells would never stop firing,

The charitable explanation is that she is suffering from hypochondria.

aquagenic urticaria comes to mind but i'm really not sure that she wouldn't be able to drink water due to it as it is an epidermal reaction.

Exactly. She has the skin reaction too, but true cases of AU (which is actually a reaction to water-soluble antigens on the skin, and not H2O) do not effect drinking. All the cases of 'water allergy' in the news contradict the symptoms of AU in that they cannot drink water also without their throat closing up and a single drop of rain can send them to the hospital.

For some reason this pops up on DailyMail every couple months or so. And it's different people, but it's always exactly the same, they cannot touch or even take a sip of even distilled water but are fine with drinking cola etc.

Why read the Daily Mail?

*Used to. Sick of articles like that one.