Neck skin darkness and blackness may be due to acanthosis nigricans, post-inflammatory hyperpigmentation, sun exposure and other reasons. 1. Acanthosis nigricans: it occurs in the folds of the skin, such as the neck, armpits, groin, etc., and the surface is rough and dry, which may be related to genetic factors, drug stimulation, endocrine diseases, etc. It may lead to the symptoms of dark neck skin. It may be related to genetic factors, drug stimulation, endocrine diseases and so on. It may lead to the symptom of dark and black neck skin. 2. Post-inflammatory hyperpigmentation: After the recovery of eczema, ringworm and other inflammatory diseases, localized hyperpigmentation will occur, leading to the symptoms of dark and black neck skin. 3. Sun exposure: long-term sun exposure may also cause local pigmentation deepening, resulting in neck skin darkness and blackness. There may be other reasons for the darkening of the neck skin, so you should go to the hospital in time for further examination and treatment as prescribed by the doctor.