What causes swollen glands?

The most common causes of swollen glands include:

• Bacterial infection, such as strep throat.
• Mouth sores or tooth infection.
• Viral infection, such as mononucleosis  or "mono."
• Skin infection.
• Ear infection.
• Sexually transmitted disease.
• Cancers such as leukemia, Hodgkin's disease, non-Hodgkin's lymphoma, and breast cancer.
• Immune system disorders, such as lupus, rheumatoid arthritis, and HIV infection.
• Side effect from a vaccine or from certain medications.