As a medical expert with a focus on dermatology, I can explain that there are several potential causes for a person's skin to appear blue. The most common reason is a condition known as cyanosis, which is a bluish discoloration of the skin and mucous membranes due to deoxygenated hemoglobin in the blood. This can occur when there is reduced oxygen supply to the body's tissues, often as a result of respiratory or cardiovascular issues.

Other causes can include:

1. Hypoxia: A state where the body or a body region has a deficient oxygen supply.

2. Congenital heart defects: These can lead to a mixing of oxygen-rich and oxygen-poor blood.

3. Smoke inhalation: Exposure to large amounts of smoke can reduce the amount of oxygen in the blood.

4. Certain drugs: Some medications can interfere with oxygen transport in the blood.

5. Frostbite: Severe cold can cause the skin to turn blue as blood flow is reduced to the extremities.

It's important to note that blue skin can be a sign of a serious medical condition and should be evaluated by a healthcare professional.

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Argyria or argyrosis is a condition caused by excessive exposure to chemical compounds of the element silver, or to silver dust. The most dramatic symptom of argyria is that the skin turns purple or purple-grey. ... The term is from Ancient Greek: ?�ѦæԦѦ�? argyros silver.read more >>