What is a classic sign of arsenic poisoning?

Mees lines in the nails are a classic sign of arsenic poisoning. These lines are transverse white bands that run across the nail and can indicate a history of systemic illness or poisoning. They are a result of the effect of toxins like arsenic on the growth of the nail matrix, leading to interruptions in nail formation during periods of exposure.

Arsenic is known for its ability to cause various symptoms, but Mees lines specifically serve as a visual indicator that can aid in diagnosing chronic exposure to the toxin. The appearance of these lines can occur weeks to months after the exposure has taken place.

In contrast, other symptoms associated with arsenic poisoning, such as vomiting (which might relate to hematemesis), gastrointestinal distress (which would encompass abdominal cramping), and headaches, are more immediate and nonspecific, reflecting acute toxic exposures rather than serving as long-term indicators. Therefore, while they may be related to arsenic poisoning, they do not provide the same diagnostic utility as the presence of Mees lines.