Your immune system functions like your body’s military or defense system, protecting it from various attackers and invaders, such as harmful bacteria, viruses, or fungi. However, conditions that involve disorder within the immune system, so that the immune system either attacks itself or substances that are not harmful to the body, are becoming increasingly common. While a primary care doctor may be able to provide basic care for such disorders within the immune system, an immunologist will be able to exercise a greater degree of expertise with treatment, evaluation, and management of immune system disorders, allergies, or asthma. While immune system disorders can be difficult to identify or diagnose, your primary care doctor may refer you to an immunologist if initial treatment methods fail to improve your symptoms. With that said, some common symptoms of immune system disorders include the following: - Abdominal pain - Difficulty concentrating - Digestive issues - Enlarged spleen - Fatigue - Hair loss - Numbness or tingling felt in the hands and feet - Recurring fever - Recurrent infections that are resistant to treatment - Skin rashes - Swollen lymph glands - Weight loss