Your immune system is your body’s built-in defense network, working nonstop to protect you from bacteria, viruses, and other harmful invaders.
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Key Takeaways:
Your immune system is your body’s built-in defense network, working nonstop to protect you from bacteria, viruses, and other harmful invaders.
Your immune system includes two main parts: the innate system you’re born with and the adaptive system that “remembers” past infections to fight them faster next time.
Healthy lifestyle habits like managing stress, eating nutrient-rich foods, getting enough sleep, exercising regularly, and limiting smoking and alcohol consumption can help keep your immune system strong.
Factors like age, sex, living environment (including exposure to children), and certain chronic conditions (such as diabetes or heart disease) can influence how well your immune system functions over time.
The immune system is the body’s natural defense network that helps to keep you healthy from things like bacteria, viruses, and parasites. It’s a complex network of cells, tissues, and organs that, when functioning properly, is able to detect and respond to many harmful invaders (i.e., protect you from illness and disease by eliminating bacteria or viruses).
Skin, mucous membranes, certain blood cells, and various organs, including the spleen and lymph nodes, are essential parts of the immune system.
The immune system has two parts: innate and adaptive. Everyone is born with an innate immune system. It’s largely informed by genetics and consists of physical barriers — mucus, fluids like sweat and tears, the closed surface of the skin — that protect against germs and other foreign bodies. It also includes chemical defenses (like stomach acid and immune signaling molecules like cytokines).
There is natural variation in innate immune defenses, which can influence susceptibility to infections. For example, if your body naturally produces thinner mucus, it could theoretically be easier for invaders to enter and potentially cause illness.
The acquired (adaptive) immune system works with the innate immune system to mount targeted responses to specific pathogens. It involves specialized white blood cells, including B cells, which produce antibodies, and T cells, which help coordinate immune responses and eliminate infected cells. The adaptive immune system can also develop immune memory, allowing the body to respond more efficiently to pathogens it has encountered before.
A component of immune health is genetic — meaning, it’s how you’re born, and you can’t do much to change it. However, there are a number of natural ways to support your immune defense and keep you as healthy as possible.
Chronic stress can suppress immune function in part by increasing cortisol levels. To reduce stress and support immune function, incorporate mindful practices such as meditation, deep breathing, yoga, or spending time in nature.
A Mediterranean-style diet filled with fruits, vegetables, lean proteins, whole grains, and healthy fats supports healthy immune function. Such foods provide essential vitamins and minerals, like zinc, selenium, and vitamins A, C, D, and E — all of which are important for immune cell activity, particularly when deficiencies are corrected. Mike Bohl, MD, a general practitioner and Senior Director of Medical Content & Authority at Hims & Hers, also recommends prioritizing foods high in fiber, omega-3 fatty acids, and probiotics.
Sleep and the circadian rhythm play an important role in regulating immune function. For most adults, the recommendation is to get at least 7 hours of sleep per night.
Exercise is important for overall health, and Dr. Bohl suggests people “engage in regular physical activity” as a strategy to keep immune defense healthy. Research shows that regular physical activity is associated with a lower risk of community-acquired infectious disease compared to the risk level among inactive adults
Smoking damages the respiratory system and weakens the immune response, making the body more susceptible to infections.
Excessive alcohol use impairs immune function, making the body more susceptible to illness or other health conditions like chronic inflammation. Keep intake moderate — ideally no more than one drink per day for women and two for men.
Research shows that conditions like obesity and diabetes have associations with compromised immune response. Maintaining a healthy weight through balanced nutrition and regular physical activity can help support more balanced immune responses.
Yep, appealing to your immune system is another reason drinking enough water is important. Adequate hydration supports circulation and normal cellular function, which indirectly supports immune health.
Having regular checkups, staying up to date on recommended vaccines, and keeping conditions like diabetes or high blood pressure under control all help keep your immune system balanced and working well. You can also test certain biomarkers to observe general immune-related patterns over time and to pinpoint any changes.
If you’re a parent whose child has gone to daycare, you already know that kids expose parents to a lot of pathogens (which can translate to feeling sick regularly). Living with children can increase your exposure to common viruses, which may influence short-term illness patterns without fundamentally strengthening or weakening the immune system.
Research shows that the immune system of people who live together (including parents) can shift to become more similar over time, reflecting shared environments and exposures rather than changes in baseline immune strength.
Furthermore, parenting can be stressful, and research suggests that chronic stress negatively impacts the immune system.
However, it’s not all doom and gloom — especially not for the long-term: Other studies suggest that increased exposure to pathogens may contribute to immune adaptation over time. However, findings are mixed: Being a parent could actually strengthen the immune system over time.
Research findings suggest that men and women have slightly different immune capabilities — more specifically, women may naturally have a stronger adaptive immune response. Men may be less likely than women to experience autoimmune diseases, but more vulnerable to infectious diseases.
Older adults are more likely to experience serious complications from illness, which is because the immune system declines with age, a process known as immunosenescence. It’s not entirely understood why this happens, though some research suggests an age-related decline in T cells lowers the efficacy of immune function.
Certain comorbidities can weaken the immune system, making it less effective at fighting infections or controlling inflammation. These include:
Diabetes
Obesity
Heart disease or hypertension
Kidney or liver disease
Chronic lung diseases (like asthma)
Cancer
Autoimmune disorders
HIV/AIDS
Malnutrition
There are many biomarkers related to your immune defense. Tracking your levels can help you and your provider notice patterns and potentially catch issues in your immune system before symptoms present. Such biomarkers include:
Basophils: A type of white blood cell that plays a role in immune and allergic responses.
Eosinophils: A type of white blood cell that helps to protect from infection and inflammation.
Lymphocytes: A specialized white blood cell that includes T cells, B cells, and natural killer (NK) cells, which have functions like fighting cancer, foreign viruses, infections, and abnormal cells.
Monocytes: A type of white blood cell that’s produced in the bone marrow and helps to fight infection.
Neutrophils: The most abundant form of white blood cell.
Systemic immune-inflammation index (SII): A calculation of the balance between the body’s immune defense and inflammation, used primarily in research and specialized clinical settings.
White blood cell count: A measure of the white blood cells in your blood.
All of these values are nonspecific and must be interpreted in a clinical context.
Your immune system is a delicate balance of genetics and external factors, and making sure it is functioning properly can help to protect you from bacteria, viruses, and disease.
A number of components, like sex, age, and more, can influence — and sometimes compromise — your immune health. The good news is that maintaining a healthy lifestyle by exercising, drinking enough water, eating a healthy diet full of antioxidants and micronutrients, and sleeping well can support immune health naturally. You can also test various biomarkers to track how your immune system is functioning.
Some supplements — like vitamin C, vitamin D, and zinc — can support immune function if you’re deficient, but they don’t “boost” your immunity beyond normal capacity. Eating a balanced diet is generally a healthy plan, but you can speak to a healthcare provider about whether supplementation may be appropriate for you.
Yes and no — it’s a myth that going outside with wet hair or being cold will make you sick. But some research shows that a drop in temperature inside the nose can kill good bacteria-fighting cells that help defend against illness. These findings do not mean that cold exposure alone causes illness.
Your immune system isn’t actually worse in the winter, but seasonal factors can increase infection risk. These factors include spending more time indoors with others and lower humidity, which allows viruses to persist longer. Together, these factors help explain why respiratory infections are more common in colder months.
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