If you tend to get colds at the same time every year, they might be seasonal allergies, according to MayoClinic.com. Hay fever and allergies to mold, dust and pet dander can cause fatigue, but so do colds and infections. Body aches aren't usually associated with allergies.

Lymph nodes are a part of your immune system. The immune system protects you from infection and other diseases. It includes your spleen, bone marrow, thymus, tonsils, adenoids, the lymph channels and the lymph nodes.

Everyone gets tired from time to time. Prolonged tiredness can cause someone to become exhausted. Long periods of exhaustion can cause or exacerbate additional conditions because it decreases the effect of the immune system in fighting off diseases.

The human immunodeficiency virus, or HIV, is a viral infection that was first identified in the early 1980s. After initial exposure to HIV, people can develop symptoms within two to four weeks, Mayo Clinic reports.

Inflammation is the pain, swelling, redness or warmth that occurs as the immune system responds to injury or illness. It may be caused by a number of conditions, such as ulcerative colitis or arthritis as well as external injuries like burns or insect bites.