The reasons for the darkening of the neck, there are genetic reasons, not to maintain personal hygiene by bathing and washing, or use moisturizers and peeling skin every period of time; to get rid of accumulated dead skin cells, in addition to impurities and toxins.
Eating low amounts of water and fluids, eating a bad diet that contains low amounts of fiber, large amounts of starchy and sugary foods, and excess weight, specifically due to the high rate of insulin in the body. Continuous exposure to the sun is specifically harmful and ultraviolet.
Reversal of bad accessories that affect the skin, as a result of the interaction of constituents with sweat and dust, and the incidence of certain diseases and problems, specifically related to thyroid gland; due to the low efficiency in the performance of its functions. Inflammation and skin problems, resulting specifically from microbes such as fungi. Pregnancy period so that hormonal changes lead to a high rate of pigmentation. Use some cosmetics or even perfumes.