Learning About Your Immune System

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What does your immune system do?

The immune system is your body's natural defense system. It helps fight infections.

Your immune system is made up of antibodies, white blood cells, lymph nodes and vessels, and other chemicals and proteins.

The parts of the immune system work together to protect your body. They attack and destroy substances that are foreign to your body, such as bacteria and viruses.


Immunity is how well you are protected from a disease. You may be born with short-term protection from certain diseases. Or you may be protected after you get an infection or a vaccine.

A vaccine helps your immune system make antibodies to fight a disease. Those antibodies will then fight the disease if you're exposed to it in the future. This helps keep you from getting sick. Or you may not get as sick.

What problems can it cause?

Your immune system can cause:

  • Allergic reactions and allergies. These happen when your immune system overreacts to something that usually doesn't harm you. For example:
    • Pollen. When some people breathe in pollen, their immune system attacks it. This causes allergy symptoms such as hay fever.
    • Medicine, chemicals, food, insect bites, or other things. An overreaction can range from mild to deadly.
  • Autoimmune diseases. These diseases happen when your immune system acts like some of your own tissues are foreign substances. The body makes antibodies and other cells that attack and destroy your tissues. These diseases include lupus and rheumatoid arthritis.

Things that can weaken your immune system

  • Substance use disorder
  • Withdrawal from alcohol or drugs
  • Certain health problems, including diabetes, cancer, HIV/AIDS, and autoimmune diseases
  • Chemotherapy or radiation
  • Some medicines, such as corticosteroids
  • Medicines that control the immune system
  • Not having a spleen
  • Stress

How can you help?

You may be able to help your immune system by having a healthy lifestyle. Make sure to:

  • Get enough sleep. How long you sleep is not as important as how you feel when you wake up. If you do not feel refreshed, you probably need more sleep.
  • Eat healthy foods. Choose fruits, vegetables, whole grains, protein, and low-fat dairy foods. Limit fat, especially saturated fat. Reduce salt in your diet.
  • Do not smoke. If you need help quitting, talk to your doctor about stop-smoking programs and medicines. These can increase your chances of quitting for good.
  • Limit alcohol to 2 drinks a day for men and 1 drink a day for women. Too much alcohol can cause health problems.
  • Take steps to control your stress and workload. Learn things to help you relax, like meditation.
  • Manage any health problems you have. For instance, control your blood sugar if you have diabetes.

The Health Encyclopedia contains general health information. Not all treatments or services described are covered benefits for Kaiser Permanente members or offered as services by Kaiser Permanente. For a list of covered benefits, please refer to your Evidence of Coverage or Summary Plan Description. For recommended treatments, please consult with your health care provider.