The itching had begun 6 months ago, stopped, and recurred. She reported no other symptoms. Examination yielded normal findings without skin changes, palpable masses, or lymphadenopathy. At the time, she was working overseas as a humanitarian aid worker and unable to get a mammogram or other evaluation without leaving the country.
Aquagenic pruritus is a skin condition characterized by the development of severe, intense, prickling-like epidermal itching without observable skin lesions and evoked by contact with water. Presentation varies from person to person. Itching most frequently occurs on the legs, arms, chest, back, and abdomen, though it can also occur elsewhere. Itching on contact with water that also includes hives is known as Aquagenic Urticaria. The exact mechanism of the condition is unknown. Some studies have suggested the itching occurs in response to increased fibrinolytic activity in the skin,   inappropriate activation of the sympathetic nervous system,  or increased activity of Acetylcholinesterase. No definitive medical test is known for aquagenic pruritus.
Itching is a common symptom and it can be caused by a number of different conditions. This guide will cover some of the most common, but it is not exhaustive -- rarer causes will not be covered. Itching, also called pruritus, is often associated with a rash, as with poison ivy.
In the past it was widely believed that pain and itching are transmitted by the same nerve pathway with the low intensity stimulation of unmyelinated polymodal C fibers resulting in sensation of pruritus whereas high intensity stimulation causing pain. In recent experiments however, stimulation of single unmyelinated C fibers led to the identification of two kinds of fibers. Stimulation of most of these fibers induces pain, whereas a small number of fibers provoke the sensation of itching.