An under or over-active immune system can lead to tiredness. When the immune system becomes over-active, it attacks the body tissues i.e. Rheumatoid Arthritis or Lupus (in extreme cases). In mild cases of immune over-activity, symptoms like sore joints, skin conditions or allergies occur. When the immune system becomes under-active, there is a lowered resistance to viruses, infections and bacteria, resulting in recurring colds and flu. Other signs are nose bleeds, poor wound healing, loss of taste, running nose, inflamed or bleeding gums, boils and sties.