15 Surprising Things That Can Affect Your Immune System

Everything from canned foods to working out too much can weaken your immune system.

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With cold and flu season in full swing, we're once again reminded how important it is to have a healthy immune system in order to fight off all those miserable bugs going around the office and our social circles. While our immune system can't protect us from every germ and virus, there are steps we can take to strengthen it. The basics—like getting enough sleep and maintaining a healthy diet—are key, but there are some unexpected things that can also have a major impact.

From laughing every day to not keeping your home too clean, here are 15 surprising things that can affect your immune system in both positive and negative ways.

1
Laughing

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The old adage that laughter is the best medicine has some truth to it, according to Lee S. Berk, DrPH, associate dean of research affairs at Loma Linda University School of Allied Health Professions. Berk has been studying the impact of laughter on mental and physical health since 1988.

"[Laughter] decreases cortisol, which then reduces stress, lowers blood pressure, increases oxygen intake, enhances the immune system, and reduces the risk of having heart disease or a stroke," Berk explained. He encourages people to laugh every day. Your immune system will thank you.

2
Optimism

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Here's another reason to keep a smile on your face. It turns out that looking on the bright side doesn't just benefit your mental health—it also impacts your physical well-being. More specifically, an optimistic outlook has been linked to a healthier immune system, according to a pivotal 1998 study published in The Journal of Personality and Social Psychology.

3
Being too clean

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When it comes to surprising things that can affect the immune system, Nikola Djordjevic, MD, a family doctor and advisor to LoudCloudHealth, says not many people are aware that keeping yourself or your home too clean can actually be detrimental to your immune system.

"Our immune response happens when we get in contact with the germs we are exposed to," Djordjevic explains. "The key is to have exposure to a reasonable amount of bacteria—not to keep your home filthy and stay unkempt yourself."

Djordjevic says cleaning your home with bleach and chemicals capable of wiping out colonies of bacteria can leave the environment sterile and germ-free. "If you're not frequently exposed to a variety of germs, your immune system cannot respond," he says. "Overprotection leaves you very vulnerable to 'attacks' by any microbes living outside of your immediate environment."

4
Living in a rural area

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Exposure to bacteria outside the home—or the lack thereof—also affects your immune system. "Growing up on a farm where the person is exposed to wider ranges of bacteria is healthier for the immune system than growing up in an urban environment," says Dean C. Mitchell, MD, clinical assistant professor at Touro College of Osteopathic Medicine.

5
Cured meats or canned foods

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Because these foods contain high levels of sodium, they can impact the immune system, according to Erin Nance, MD. "In a study examining the effects of excessive salt intake on immune function, they found that a high salt-diet had a potential to trigger an excessive immune response," she explains.

Furthermore, Nance says that high salt intake has also been shown to alter immune function by suppressing regulatory T cells, which help with the body's anti-inflammatory response.

6
Too much exercise

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It's no surprise that not getting enough exercise can weaken your immune system—but Mitchell says over-exercising can also be harmful. "Too much exercise increases Interleukin-6 (IL-6)" and depresses immune system function, he explains.

7
Loss and grief

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Losing a loved one is a devastating experience and long-term grief can impact your immune system, according to a 2012 study published in Dialogues in Clinical Neuroscience. Researchers found that "an unresolving grief response may be a risk factor for altered immune response," but this effect is not immediate. Participants characterized as having a "harm-avoidant temperament and long-lasting dysphoric mood" six months after the unexpected loss of a loved one had a more reduced immune system response than participants who exhibited lower grief levels.

8
Loneliness

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A 2015 study published in Proceedings of the National Academy of Sciences found that "perceived social isolation" (loneliness) is linked to immune system changes. Steve Cole, the study's lead author, observed that when participants felt lonely, they had significantly higher levels of the hormone norepinephrine in their blood. When a person is in a life-threatening situation, norepinephrine courses through the blood and shuts down immune system functions, such as viral defenses. Meanwhile, the production of white blood cells called monocytes increases.

"It's this surge in these pro-inflammatory white blood cells that are highly adapted to defend against wounds, but at the expense of our defenses against viral diseases that come from close social contact with other people," Cole explained.

9
Chronic stress

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"Our stress hormones evolutionarily were only meant to be activated in a time of serious threat, often referred to as a 'flight or fight' response," says Tania Elliott, MD, an associate attending at NYU Langone Health. But chronic stress means lower levels of these hormones are constantly circulating in your blood. Elliott explains that this stimulates chronic inflammation of a host of organs, which in turn fatigues our immune system.

10
Bottling up emotions

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According to a 2018 study published by Brain, Behavior, and Immunity, negative moods can affect immune response functions and increase the risk of exacerbated inflammation. That same year, researchers at Penn State found that teenagers who suppressed negative emotions were more likely to "produce more pro-inflammatory cytokines, molecules that signal to other cells that there is a threat present and that the body's immune system needs to kick into gear." A high level of cytokines suggests that the immune system isn't functioning the way it should be.

11
Alcohol use

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Drinking has a negative effect on the immune system, particularly when it's in excess. "Alcohol use may weaken the immune system by changing the balance of normal microorganisms that live in a healthy body, leading to increased inflammation," says Chirag Shah, MD, co-founder of Push Health.

Additionally, Shah says that alcohol use may impair specific cells in the immune system, including macrophages and monocytes, and "reduce the body's capacity to reduce the normal inflammatory response when it needs to be turned off."

12
Nicotine use

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It's no secret that nicotine use can wreak havoc on your respiratory system, but research published in 2009 by Acta Pharmacologica Sinica found that it can also harm your immune system. According to the study, nicotine use affects both branches of the immune system and "produces an altered immune response that is characterized by a decrease in inflammation, a decreased antibody response, and a reduction in T cell-receptor-mediated signaling."

13
Age

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Mitchell says that age also has a bearing on your immune system. "Very young infants are more prone to infections because their antibodies haven't fully developed, and the elderly have decreased immunity because their antibodies have waned," he explains.

14
Medications

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Certain medications can negatively affect your immune system. Mitchell notes that acid-blocking heartburn medications like Prilosec and Nexium decrease stomach acid and allow yeast and bacteria to overgrow, which in turn lowers immunity.

Nance says corticosteroid medications also impact the immune system. Many people take some form of oral steroids to treat conditions like asthma, arthritis, and autoimmune disease. "Steroids decrease inflammation by reducing the chemical activity of the body's immune system," Nance explains. "Glucocorticoids at high concentrations inhibit the production of B Cells and T Cells, the main components of the body's immune system."

15
Oral hygiene

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Daniel Naysan, DDS, a dentist in Beverly Hills, says there's a significant connection between oral health and your immune system. "Risk factors such as periodontal disease, decay, [and] oral infections elicit the white blood cells, which are the defense system to our immune system [and] are activated to help fight these oral diseases," Naysan explains. If these oral infections aren't treated, your immune system may become compromised and weaken over time.

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