Causes of inguinal lymphadenitis include:

• Bacterial infections:
• Skin infections
• Sexually transmitted diseases
• Viral infections

Bacteria are normally present on the surface of the skin. The bacteria are harmless because the surface of the skin acts as a protective barrier. When this barrier is broken, bacteria can enter the skin beneath the surface and start to grow. Streptococcus or staphylococcus are the most common bacteria that cause inguinal lymphadenitis.
Lymphadenitis from bacterial infections usually occurs after an injury to the skin. The injury allows the bacteria to invade the tissue beneath the skin, and then spread to the lymph glands.

Injuries that may lead to bacterial infections include:

• Animal bites
• Burns
• Cat scratches
• Marine stings
• Puncture wounds
• Abrasions
• Lacerations

Sexually transmitted diseases that cause inguinal lymphadenitis include:

• Chancroid
• Chlamydia
• Gonorrhea
• Herpes genitalis
• Lymphogranuloma venereum
• Syphilis

Viral infections that cause inguinal lymphadenitis include:

• Mononucleosis
• Cytomegalovirus
• Varicella
• Adenovirus infections