Hyperpigmentation of the skin Axillary hyperpigmentation Darkened underarms Underarm hyperpigmentation Dark axillae An abnormal increase in skin coloration affecting one or both axillae, resulting in the affected skin appearing darker than the surrounding skin. Hyperpigmentation in the axillary is more common than in other parts of the skin because of irritation and inflammation usually caused by body folds, friction, hair plucking, shaving, deodorants, and using whitening agents. Axillary hyperpigmentation may manifest as hyperpigmented macules or plaques, which can affect the dermis, epidermis, or both.