Bacteria, such as streptococcus or staphylococcus, are the most common causes of lymphadenitis.

Viral infections can also cause swelling of lymph nodes. Lymphadenitis from bacterial infections usually occurs after an injury to the skin.

Skin injuries that may cause axillary lymphadenitis include:

• Animal bites
• Burns
• Abrasions
• Marine stings
• Puncture wounds
• Scratches and cuts

Diseases that cause axillary lymphadenitis include:

• Skin abscess
• Cancer
• Cellulitis
• Tuberculosis
• Lymphoma
• Mononucleosis
• Cat scratch disease