Medically reviewed by Brendan Camp, MD Hyperpigmentation (skin that is darker than the surrounding skin) in the underarms can have several causes. Acanthosis nigricans (AN) is a common cause. AN ...

It's common in the armpits, under the breasts, and in the folds of the groin and abdomen. The rash is often caused by yeast, fungi, or bacteria that love being in a damp environment. These germs ...

It can cause an armpit rash that becomes raw or cracks open ... Intertrigo can also lead to secondary infections when bacteria or yeast gets trapped in the skin folds. Contact dermatitis is ...