What causes the face to turn black?

The causes of facial darkening can be divided into two major categories: physiological and pathological.

Physiological causes:

1. Sun exposure: Prolonged exposure to sunlight can promote the formation of melanin in the skin, leading to facial darkening. It is recommended to take sun protection measures when going outdoors.

2. Environmental temperature changes: For example, sudden cold weather or transitioning from a warm to a cold environment may cause facial darkening. This is usually temporary and can improve after acclimatization.

3. Chronic late-night activities: Long-term sleep deprivation due to staying up late can affect skin metabolism, causing the skin to become dull and even darken. It is recommended to ensure adequate sleep daily.

Pathological causes:

1. Hepatitis B: Patients with hepatitis B may experience impaired liver function and abnormal metabolism, which can lead to skin pigmentation and a grayish facial appearance.

2. Other diseases: Conditions such as cirrhosis, adrenal insufficiency, chronic renal insufficiency, chronic cardiopulmonary insufficiency, and liver cancer may also cause facial darkening.

In addition, certain skin conditions such as freckles, melasma, and post-inflammatory hyperpigmentation can lead to localized or overall skin darkening. If the face suddenly darkens accompanied by other symptoms, it is recommended to seek timely medical attention for diagnosis and treatment.