Internal cause:

1. Heredity

Skin is different from race and skin of different parts of an individual. Its color is different. This is determined by heredity.

2, endocrine factors

Pregnancy, irregular menstruation, oral contraceptives, etc. can increase the differentiation of melanin in the epidermis, causing skin coloring.

3. Chronic diseases

Some chronic diseases such as chronic infection, tumor, lupus erythematosus and cirrhosis can cause skin coloring.

External cause:

1, sun exposure

There are two basic reactions in the skin after sun exposure: one is the expansion of the dermal vessels, and the other is the alteration of the skin's pigment attack. Two.

2. The improper use of cosmetics affects whitening

Improper manipulation of cosmetics can attack the damage of contact dermatitis, pigmentation, and so on. The dull skin should be particularly cautious when manipulating cosmetics. In medical mission, patients often encounter allergies and redness due to improper use of cosmetics.

3, the skin of acute and chronic inflammation of the skin after acute, chronic inflammation is likely to attack pigmented cool, with the lapse of Kung Fu most can gradually become shallow or disappear, it is also extremely likely to not retreat temporarily. For example, after the healing, there will be obvious gray brown stains on the face, which is hard to fade.