What is causing a hard, red, painful lump under my armpit?
Not Medical Advice: A hard, red, painful lump under the armpit could be a cyst or an infection caused by the use of antiperspirants or by shaving. It could also be an abscess under the skin or swollen lymph nodes caused by cancer, vaccinations, or bacterial or viral infections. Cysts or lumps caused by viral infections should disappear without treatment. Unexplained lumps need medical attention.
Updated on Wednesday, February 01 2012 at 03:48PM EST