The causes of melanin deposition on the neck skin are external factors and intrinsic factors, and there are great differences in the treatment methods. In terms of extrinsic factors, such as prolonged UV exposure, intrinsic factors such as acanthosis nigricans, liver and kidney diseases and post-inflammatory hyperpigmentation: 1. UV exposure: prolonged sun exposure causes local melanin deposits, which can improve on their own after a period of time if they are well protected from the sun, and it is recommended to use regular skin care products with moisturizing, nourishing and whitening effects to help the skin tone recover. If the neck skin is exposed to the sun for a long time without protection, in addition to melanin deposits, it will increase the probability of various skin diseases; 2, acanthosis nigricans: in addition to the darkening of the neck, the local skin can also appear dry, rough, or superfluous appear. There are various causes of acanthosis nigricans, such as genetics, obesity, and the use of certain drugs. For treatment, commonly used medications include vitamin A, salicylic acid, cod liver oil, etc. Laser treatment can also be considered. If it is caused by obesity, you also need to control your diet and reduce your weight. If the side effects are caused by the application of certain drugs, it is recommended to consult the doctor whether it is necessary to change the drugs or stop taking them. If it is secondary to some disease, it is recommended to actively treat the primary disease. Daily attention should be paid to not scratching the affected area to avoid aggravation; 3. Liver and kidney diseases: such as hepatitis, hypoadrenocorticism, causing changes in the level of estrogen and adrenocorticotropic hormone in the body, resulting in hyperpigmentation. It is necessary to systematically treat the original disease, such as hepatitis can take antiviral drugs, liver protection drugs, etc., and hyperalgesia requires hormone replacement therapy; 4, post-inflammatory hyperpigmentation: is one of the common sequelae of acute or chronic inflammation of the skin, can be treated with topical drugs, such as hydroquinone, vincristine, etc., can also be treated with fractional laser, chemical peeling and other ways.