“Why Is My Immune System So Weak?” Expert Doctors Share 8 Major Causes

Updated: Jun. 24, 2024

If you're catching colds or feeling under the weather more often during this season, a few straightforward changes to your lifestyle might be just what you need to combat these recurring illnesses.

People look at brochure and use smart phones while waiting
SDI Productions/Getty Images

Do you often ask yourself, “Why am I always the one getting sick? Why is my immune system so weak?” These questions might linger in the back of your mind, especially if you’re frequently down with the latest cold or flu. If this resonates with you, know that you’re not alone.

A considerable number of individuals contend with what appears to be a compromised immune system. Perhaps you’re constantly feeling fatigued, dealing with persistent stomach issues, or you’ve noticed that minor cuts or bruises are unusually slow to heal. Understanding the root cause of these symptoms is critical in seeking effective remedies.

To help keep you healthy this virus season, we asked experts to share some prevalent factors that could be weakening your body’s innate protective mechanisms.

I need to find a way to cope with this stress
Nicola Katie/Getty Images

“Why is my immune system so weak?”

1. Stress

Yes, stress. It’s not just a mental or emotional issue—it’s a physical one too. When you’re stressed, your body produces stress hormones like cortisol, which can suppress the immune system. Chronic stress, in particular, can lead to an ongoing state of immune suppression, making you more susceptible to infections. A key aspect of this suppression includes a reduction in your body’s lymphocytes.

Nadia Hasan, DO, a family physician at Penn Medicine, explains, “Stress decreases the body’s lymphocytes, the white blood cells that help fight off infection. The lower your lymphocyte levels, the more you’re at risk for viruses like the common cold.”

And it’s not just about feeling anxious or overwhelmed—even chronic low-grade stress can have this effect.

Want to Stop Stress? A New Study Found This Solution Was More Powerful Than Meditation

Man eating cheeseburger, personal perspective view
Alexander Spatari/Getty Images

2. Diet

Harvard Health says there’s scientific truth to the saying “You are what you eat.” If you often wonder “why is my immune system so weak?” it might be your diet. A diet lacking in essential nutrients can impair the production and activity of immune cells and antibodies. In particular, a deficiency in vitamins A, C, E, and minerals like zinc and selenium can weaken your immune response. On the flip side, a diet high in processed foods, sugar, and alcohol can lead to inflammation, further compromising your immune health.

5 Worst Foods for Your Immune System, Say Experts

girl has pleasant dreams and health sleep
yellowpicturestudio/Getty Images

3. Sleep

When you sleep, your body produces and distributes important immune cells like cytokines, T cells, and interleukin 12. If you’re not getting enough quality sleep, your immune system doesn’t get the chance to fully regenerate, leaving you more prone to infections. Experts recommend 7-9 hours of sleep per night for optimal immune function.

7 Secret Ways Doctors Boost Their Immune Systems

Woman running exercise on track treadmill
Sorapop/Getty Images

4. Exercise

Marci Goolsby, MD, Co-Director of the Women’s Sports Medicine Center at the Hospital for Special Surgery in New York City, highlights an important aspect of exercise and immune health in a blog post: While regular physical activity is beneficial for boosting the immune system, there’s a balance to be maintained. Overdoing it with intense exercise without proper recovery can lead to a decrease in immune function, a condition often referred to as “overtraining syndrome.”

Moderate, regular physical activity, on the other hand, is beneficial. It helps circulate your blood and lymphatic fluid, transporting immune cells throughout your body more efficiently.

Why 20 Minutes Is the Magic Number for a Healthier Immune System

Pouring Some Tap Water Into Her Glass
vitapix/Getty Images

5. Hydration

Water plays a vital role in supporting your immune system. A fluid in your circulatory system called lymph, which carries immune cells around your body, is largely made up of water. Dehydration can slow down the movement of lymph, sometimes leading to an impaired immune system.

The 3 Best Hydrating Beverages That Aren’t Water, from a Certified Sports Dietitian

Period pain is totally lame
LaylaBird/Getty Images

6. Gut health

Questioning “Why is my immune system so weak?” The answer might lie in your gut. Surprisingly, about 70% of your immune system resides in your gut, as outlined by a 2021 study. A healthy gut flora is essential for a robust immune response. An imbalance in gut bacteria can lead to reduced immunity and increased susceptibility to pathogens. Consuming probiotics and prebiotics can help maintain a healthy gut flora.

Eating This Nut Will Help Your Gut and Reduce Inflammation, New Study Says

African woman hand holding pills and medicine
Ridofranz/Getty Images

7. Medical conditions and medications

Certain chronic medical conditions, ranging from diabetes to HIV/AIDS, as well as medications, particularly immunosuppressants and certain cancer treatments, can weaken the immune system. If you have a chronic condition or are on medication, talk to your doctor about how to best support your immune health.

Additionally, your genetic makeup plays a role in the strength of your immune system. Some people are born with stronger immune systems, while others might have genetic conditions that affect their immunity.

11 Best Foods for Your Immune System

Businesswoman Walking In The Rain
Willie B. Thomas/Getty Images

8. Environmental factors

Exposure to pollutants, toxins, and even drastic changes in weather can strain your immune system. Living in areas with high pollution or frequent exposure to toxins can lead to chronic inflammation and weaken your body’s defenses.

Lung Cancer Is Worst in These 8 States, New National Report Says

A young woman lying on bed. Feeling sick
Roos Koole/Getty Images

How to strengthen your immune system

If you have a weakened immune system, there are effective and straightforward strategies to steer it back to health. The Cleveland Clinic provides some valuable advice:

Start with a balanced diet enriched with fruits, vegetables, whole grains, lean proteins, and healthy fats. Nutrient-rich foods such as citrus fruits, garlic, ginger, and leafy greens are particularly beneficial for boosting immunity. Pair this with regular, moderate exercises like brisk walking or yoga, which are great for enhancing your body’s infection-fighting abilities.

Equally important are adequate sleep and hydration. Strive for 7-9 hours of quality sleep nightly and ensure you’re drinking enough water for optimal immune system performance. Managing stress is also critical. Practices like meditation and deep breathing can significantly reduce the adverse effects of stress hormones on your immune system.

In addition, moderating alcohol intake and steering clear of smoking are essential. Excessive alcohol can impair the immune system’s ability to ward off infections, while smoking introduces harmful toxins that weaken immune defenses, especially in the respiratory system. Both habits can disrupt your body’s natural immune response, making it more susceptible to illnesses.

For more wellness updates, subscribe to The Healthy @Reader’s Digest newsletter and follow The Healthy on Facebook and Instagram. Keep reading: