What are autoimmune diseases?Your immune system is made up of organs and cells meant to protect your body from bacteria, parasites, viruses and cancer cells. An autoimmune disease is the result of the immune system accidentally attacking your body instead of protecting it. It's unclear why your immune system does this.There are over 100 known autoimmune diseases. Common ones include lupus, rheumatoid arthritis, Crohn’s disease and ulcerative colitis.Autoimmune diseases can affect many types of tissues and nearly any organ in your body. They may cause a variety of symptoms including pain, tiredness (fatigue), rashes, nausea, headaches, dizziness and more. Specific symptoms depend on the exact disease.AdvertisementCleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. PolicyHow do autoimmune diseases work?Experts don’t know why your immune system turns on you. It’s like it c...
