Unrelenting stress, chronic allergies, chronic infections can exhaust the immune system. Other causes of a weakened immune system are vaccinations and immunizations against common childhood and epidemic diseases. The thymus gland seems to be the most affected by this weakening. The thymus gland is especially important due to its production of T-helper cells. Prolonged stress, or toxic exposure to chemicals or radiation can weaken the immune system.
Severe infections can both result and cause it.
Lack of proper rest is yet another cause. Yet another cause are nutritional deficiencies. Some natural healing specialists believe that any infectious disease may be considered an immune deficiency problem. The taking of aspirin has been linked to Reye's syndrome, asthma, low birth weight and birth defects. Meat contains hormones, antibiotics, and bacteria which brings on disease.