An ache in the armpit may indicate the presence of an abscess, which is a tender, fluid-filled lump caused by the body's inflammatory response, states WebMD. Other causes of aches in the armpit include swollen lymph nodes.
The presence of an abscess in the armpit is not cause for alarm. The armpit is one of the most common locations for an abscess to appear. Other common locations include around the anus and vagina as well as around the base of the spine, according to WebMD.
Abscesses are easy to identify by the way they feel. They appear on the skin as a tender mass that is painful to touch, often warmer than the surrounding skin, and filled with fluids, such as pus and other debris. Smaller abscesses can benefit from the application of a warm compress for about a half-hour, four times a day, suggests WebMD.
In some instances, an abscess comes to a head on its own and ruptures, releasing the fluid inside. In this case, no treatment is required though the individual should clean the affected area and cover it to prevent further infection. Not all abscesses come to a head. In this case, the individual must either drain the abscess or seek medical help in draining it to prevent infection of the surrounding tissue and bloodstream, states WebMD.