Histamine is a potent vasodilator and increases vascular permeability, contributing to the vasodilatory shock and hypotension seen in anaphylaxis. It also causes bronchoconstriction but is primarily responsible for the vasodilatory component.

ETEC are the principal cause of traveler’s diarrhe1) They produce both a heat-labile toxin (LT) and a heat-stable toxin (ST) that act on the intestinal mucos1) The LT is similar to cholera toxin and increases intracellular cGMP levels, leading to enhanced fluid and electrolyte secretion into the lumen and thus diarrhe1) The ST acts by a different mechanism but also enhances fluid and electrolyte secretion.

A gastrinoma is a non-beta cell tumor that autonomously produces large amounts of gastrin, leading to hypergastrinemia and increased acid secretion in the stomach, resulting in severe peptic ulcers.

The chronic non-healing nature of the ulcer and its location on the lower leg in an individual with a history of alcoholism are more consistent with a neuropathic ulcer. Neuropathy due to chronic alcohol use can lead to loss of protective sensation and poor blood supply, resulting in these types of ulcers.

Cystic fibrosis is a genetic disorder affecting the lungs and other organs, leading to respiratory infections and digestive issues, including steatorrhoea and electrolyte imbalances.