Darkening of the armpits can occur in a variety of ways, usually mostly due to abnormal hormone levels. In this case, in addition to the darkening of the armpits, the groin and the neck may also become darker. In addition to the darkening of the skin due to hormonal abnormalities, it can also be caused by obesity, especially in the case of obesity-induced acanthosis nigricans, which results in darkening of the skin in the armpits and velvet-like hyperplasia. There is also a kind of chronic eczema in the armpit and the appearance of inflammation after the pigmentation, will also appear the skin darkening performance.