Hair loss in the armpits, also known as axillary hypotrichosis, is a condition characterized by a reduction or complete absence of hair in the armpit region. It can be unilateral, affecting only one armpit, or bilateral, affecting both armpits. Axillary hypotrichosis can be a normal variation or a sign of an underlying medical condition.
In some cases, hair loss in the armpits can be a temporary side effect of certain medications, such as chemotherapy or hormone therapy. It can also be a symptom of hormonal imbalances, such as hypothyroidism or hypopituitarism. In rare cases, axillary hypotrichosis can be a sign of a genetic disorder, such as ectodermal dysplasia or Down syndrome.