Which condition is a sign of cyanosis?

Cyanosis is characterized by a bluish discoloration of the skin and mucous membranes, which occurs when there is insufficient oxygen in the blood. This bluish tint, particularly noticeable in the lips and skin, is a direct indicator of hypoxia or poor oxygenation.

The presence of cyanosis suggests that the blood is not delivering adequate oxygen to body tissues, which can be due to various respiratory or cardiovascular issues. In this context, the bluish coloration is a critical sign that healthcare providers look for when assessing a patient's oxygen levels and overall respiratory health.

The other conditions listed involve different skin color changes that do not indicate cyanosis. For example, reddish skin can indicate inflammation or fever, yellowing skin suggests jaundice, typically related to liver dysfunction, and pallid skin signifies paleness that may be due to anemia or shock, all of which are distinct from the bluish hue associated with cyanosis.