Most armpit pain is caused by an infection. The infection may be localized sweat gland inflammation, or folliculitis forming localized swelling and pain; it may also be sebaceous gland inflammation, which can also cause armpit pain. Of course, lymphadenitis in the armpit can also cause painful symptoms. In addition, there is also the possibility that herpes zoster may cause neuropathic pain in the armpit. Herpes zoster is usually found in the periphery of the armpit or in the upper extremity of that side, which can also cause pain in the armpit, and in some cases, the herpes has not fully formed when the armpit pain is present. Therefore, a differential diagnosis is needed to determine whether herpes zoster or another bacterial infection is present and causing the pain.