Zits in armpits? one particular zit is like a pimple that won't go away and is tender and feels like a constant open wound.

Infections: Armpits are common places to get skin infections. Most skin infections do not clear on their own. They need to be treated.

Infected glands: This is an area that you have both hair roots and the sweat/odor glands that can also become infected.Mechanical action of clothing rubbing the area, shaving, etc can irritate the skin. Surface germs like staph can invade the pores and trigger zit like infections. Sometimes gentle heat can improve circulation enough to self heal, but many will need oral antibiotics.