Causes, Symptoms, and Risk Factors

Some causes of a weak immune system include conditions like cancer, diabetes, and pregnancy. People who take corticosteroids or immunosuppressants can also have a weakened immune system.

Your immune system is your body’s defense mechanism against viruses, bacteria, and other microbes that cause illness. In most healthy people, the immune system works as intended, but sometimes it overreacts or doesn’t work as it should. People with weak immune systems are more susceptible to illness as a result.

White blood cells are immune cells that circulate in your body to prevent and fight infection. These blood cells mostly do their job in healthy people, but certain health conditions, procedures, and medications can affect their function.

Immunodeficiency (weak immune system) is characterized as either primary (present at birth) or acquired (developed later in life).

Medications

Medications can weaken your immune system. These medications include corticosteroids, immunosuppressants, and tumor necrosis factor (TNF) inhibitors.

Health Conditions

Many health conditions can weaken your immune system. Conditions that can cause a weak immune system include:

• Alcohol use disorder
• BENTA disease
• Cancer
• Common variable immunodeficiency
• Diabetes
• Human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS)
• Immunoglobulin (IgA) deficiency
• Inherited autoimmune conditions like lupus or rheumatoid arthritis (RA)  
• Liver or kidney disease  
• Multiple myeloma, a type of blood cancer
• Obesity
• Organ or tissue transplant
• Pregnancy

Age

Your age impacts how well your immune system functions. Newborns and young children have immune systems that are still developing, making them less able to fight off infection. As you age, particularly after mid-life, immune function often declines.

A weakened immune system is an expected part of getting older, but there are things you can do to enhance your immune function, like getting adequate sleep, keeping active, and eating a nutritious diet.

Lifestyle Factors

Lack of regular exercise, inadequate sleep, poor nutrition, heavy alcohol use, smoking, and drug misuse can all contribute to a weakened immune system. In contrast, eating a balanced diet, exercising regularly, getting enough rest, and limiting alcohol, smoking, and drug use can have a positive impact on your immune system.

Here are some signs of a weak immune system:

• You have digestive problems: Long-lasting digestive problems like chronic diarrhea may indicate a weak immune system.
• You get recurrent or chronic infections: You may have a weak immune system if you get the same kind of infection repeatedly or have an infection that won’t clear with typical treatments (such as persistent thrush or fungal infections).
• You get unusual infections: You may have a weak immune system if you get less common and more severe infections that most people don’t get, such as bacterial infections like tuberculosis or parasitic infections like toxoplasmosis.
• Your cuts and scrapes heal slowly: Poor wound healing can be a sign of an immune deficiency.
• You are getting sicker and staying sicker longer: Different people take different amounts of time to recover from an illness. You might have a weak immune system if you have an infection that’s taking much longer to clear up than usual or are always sick.

Other red flags for immune deficiency include unexplained weight loss or lack of weight gain, swollen lymph nodes or spleen, and low white or red blood cell counts.

Certain factors can increase your risk of having a weak immune system, including:

• Being a transplant recipient
• Having an autoimmune disorder
• Having chronic stress
• Having a family history of immune deficiency or early deaths from infection
• Taking medications known to suppress immune function
• Undergoing treatment for cancer
• Prolonged use of corticosteroids

Prevention is critical for people with a weak immune system. Healthcare providers recommend that you wear a high-quality mask in public areas and get vaccinated against viral infections like COVID-19 and the flu.

Other ways to protect yourself include:

• Avoid contact with people who are sick with something they can spread to others.
• Ensure your home environment is clean by wiping down and sanitizing often-touched surfaces.
• Get plenty of sleep.
• Keep current on all your recommended vaccinations, and ask your healthcare provider which ones are safe for you. (Live vaccines aren’t safe for people who are immunocompromised or who have immunodeficiency.)
• Practice healthy habits like eating a nutritious diet, exercising regularly, and reducing stress and anxiety.
• Protect yourself from food and waterborne illness by thoroughly cooking your food and ensuring your water is clean and safe.
• Wash your hands with soap and water often.

Causes of a weak immune system range from lifestyle factors like inadequate sleep to health conditions like cancer, diabetes, and pregnancy. Medications like corticosteroids or immunosuppressants can also weaken your immune system and make you more susceptible to illnesses. 

Talk to a healthcare provider about ways to protect yourself and your loved ones if you have a weak immune system. Protective measures can include getting plenty of sleep, staying up-to-date with vaccinations, and washing your hands regularly.