Underarm hyperpigmentation or acanthosis nigricans, is a common skin condition characterized by areas of dark pigmented, thick skin. Although many of us may suffer from dark underarms, the solution to the problem might be a lot less complicated than you may think.
The repetitive irritation and friction caused by shaving can produce more melanin. This process promotes the development of greyish-brown or black pigmentation in the underarm area. Applying deodorant right after shaving actually promotes more irritation. This irritation causes the skin to get thicker and thicker to protect itself, also causing color changes to the affected area.