What is the characteristic symptom indicating carbon monoxide poisoning?

The characteristic symptom indicating carbon monoxide poisoning is cherry red skin. This distinctive coloration occurs because carbon monoxide binds with hemoglobin in the blood more effectively than oxygen, forming carboxyhemoglobin. This binding reduces the ability of blood to carry oxygen, leading to hypoxia. As the blood becomes saturated with carbon monoxide, it can produce a characteristic bright red or cherry red appearance, especially evident in the lips and skin. Although not all individuals with carbon monoxide poisoning will exhibit this symptom, it is classically associated with the condition and can be a significant indicator in clinical settings.

The other symptoms, while they may occur in various poisoning or medical conditions, are not specific to carbon monoxide poisoning. Pinpoint pupils can indicate opioid overdose or other types of poisoning, flank pain is more commonly associated with renal issues, and abdominal cramping is not typically linked to carbon monoxide exposure. Thus, cherry red skin serves as a primary diagnostic sign for recognizing carbon monoxide poisoning effectively.