An autoimmune disease is a condition in which your immune system mistakenly attacks your body.

The immune system normally guards against germs like bacteria and viruses. When it senses these foreign invaders, it sends out an army of fighter cells to attack them.

Normally, the immune system can tell the difference between foreign cells and your own cells.

In an autoimmune disease, the immune system mistakes part of your body — like your joints or skin — as foreign. It releases proteins called autoantibodies that attack healthy cells.

Some autoimmune diseases target only one organ. Type 1 diabetes damages the pancreas. Other diseases, like lupus, affect the whole body.

Why does the immune system attack the body?

Doctors don’t know what causes the immune system misfire. Yet some people are more likely to get an autoimmune disease than others.

Women get autoimmune diseases at a rate of about 2 to 1 compared to men — 6.4 percent of women vs. 2.7 percent of men. Often the disease starts during a woman’s childbearing years (ages 14 to 44).

Some autoimmune diseases are more common in certain ethnic groups. For example, lupus affects more African-American and Hispanic people than Caucasians.

Certain autoimmune diseases, like multiple sclerosis and lupus, run in families. Not every family member will necessarily have the same disease, but they inherit a susceptibility to an autoimmune condition.

Because the incidence of autoimmune diseases is rising, researchers suspect environmental factors like infections and exposures to chemicals or solvents might also be involved.

A “Western” diet is another suspected trigger. Eating high-fat, high-sugar, and highly processed foods is linked to inflammation, which might set off an immune response. However, this hasn’t been proven.

Another theory is called the hygiene hypothesis. Because of vaccines and antiseptics, children today aren’t exposed to as many germs as they were in the past. The lack of exposure could make their immune system overreact to harmless substances.

Autoimmune disease symptoms

The early symptoms of many autoimmune diseases are very similar, such as:

• fatigue
• achy muscles
• swelling and redness
• low-grade fever
• trouble concentrating
• numbness and tingling in the hands and feet
• hair loss
• skin rashes

Individual diseases can also have their own unique symptoms. For example, type 1 diabetes causes extreme thirst, weight loss, and fatigue. IBD causes belly pain, bloating, and diarrhea.

With autoimmune diseases like psoriasis or RA, symptoms come and go. Periods of symptoms are called flare-ups. Periods when the symptoms go away are called remissions.

Tests that diagnose autoimmune diseases

No single test can diagnose most autoimmune diseases. Your doctor will use a combination of tests and an assessment of your symptoms to diagnose you.

The antinuclear antibody test (ANA) is often the first test that doctors use when symptoms suggest an autoimmune disease. A positive test means you likely have one of these diseases, but it won’t confirm exactly which one you have.

Other tests look for specific autoantibodies produced in certain autoimmune diseases. Your doctor might also do tests to check for the inflammation these diseases produce in the body.

How are autoimmune diseases treated?

Treatments can’t cure autoimmune diseases, but they can control the overactive immune response and bring down inflammation. Drugs used to treat these conditions include:

• nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (Motrin, Advil) and naproxen (Naprosyn)
• immune-suppressing drugs

Treatments are also available to relieve symptoms like pain, swelling, fatigue, and skin rashes.

Eating a well-balanced diet and getting regular exercise can also help you feel better.