I'm a Healthy Person—So Why Am I Always Sick?

Here's what really determines the strength of your immune system—and what you can do to help it function at its best.

Even if you take care of yourself so that you're generally healthy, there's always the possibility of getting sick—even more often than you might expect. But how often you get sick as a healthy individual comes down to how your body functions.

As an editor at Health, I practice what we preach. I get 7 to 8 hours of sleep most nights, I make it to my favorite workout classes regularly, and I eat all of my servings of fruits and vegetables every day (okay, I leave room for wine and dessert too).

Yet every year, I manage to come down with several colds, bouts of strep throat, and stomach bugs. I even got shingles a few years ago. My burning question: Why do I keep getting sick, despite doing everything "right"?

The short answer: I may just have a slightly weaker immune system. "I have some perfectly healthy patients who get five to six upper respiratory infections—aka, the common cold, or more rarely, full-blown influenza—a year, and others with the same health profile who hardly ever get sick," said Holly Phillips, MD, an internal medicine physician in New York City and author of The Exhaustion Breakthrough. "It doesn't seem fair, and honestly, it's not."

Even more, some individuals are also thought to be especially resistant to certain bacterial and viral infections. "Immunologists refer to them as having 'super-immunity,' and their genetic makeup is the focus of an entire field of research," Dr. Phillips said.

What Factors Into Your Level of Immunity?

Your immunity is determined by several factors. Genetics play a significant role, said Paolo Boffetta, MD, professor of medicine, hematology, and medical oncology at Icahn School of Medicine at Mount Sinai Hospital in New York City. "Immunological genes are many and complex, and your immune response depends on their combined performance," Dr. Boffetta explained.

Related to that is your innate immunity. A person's innate immunity is essentially the bodily defense system a person is born with, per MedlinePlus, and includes aspects such as cough reflexes, mucus, and stomach acid.

Experts also believe that you build up immunity while you are young or possibly even before you are born (which may happen through passive immunity, where antibodies produced beyond your body end up as part of your immune system like in the case of pregnancy). "There are factors during infancy and childhood, and perhaps also in utero, that contribute to the development of the immune system, but they are not fully understood," Dr. Boffetta said.

One standout theory for why some people may just be more susceptible to illness is the hygiene hypothesis—the idea that the more bacteria and viruses you come into contact with as a kid, the "smarter" your immune system becomes. The thinking is that "keeping kids extra clean and smothering them in hand sanitizer may cause more harm than good in the long run," Dr. Phillips explained.

What Can Affect Your Immune System?

On top of that, there are lifestyle factors that can all weaken your immune response and lead to more frequent infections, Dr. Boffetta noted.


The ability of your body and brain to respond to challenges or demands is considered stress, according to MedlinePlus. Short-term stress is generally less harmful to your health. However, being stressed for long periods of time can affect your immune system: You may find that you get sicker more often since that long-term stress might turn into recurrent health issues or health problems (e.g., diabetes, anxiety).


Obesity can also play a part in a weakened immune system. Researchers of a BMJ Open study published in October 2019 investigated the relationship between self-reported health problems, obesity, and absences due to sickness for 21,608 employees. They found that individuals who reported health issues (e.g., fatigue, sleep problems, stress) and had higher BMIs were more likely to spend more time absent from work due to sickness.

Alcohol Use

Having a drink or two on occasion may not cause a lot of issues for your immune system. However, engaging in frequent or chronic heavy drinking can decrease the efficiency of your immune system. Per a February 2016 article published in Progress in Neuro-Psychopharmacology and Biological Psychiatry, "chronic heavy drinking is associated with a decreased frequency of lymphocytes and increased risk of both bacterial and viral infections."


A Scientific Reports study published in February 2021 found that air pollution can have a negative impact on both immune and cardiovascular systems at a young age. Thus, environmental factors, such as pollutants and toxins, may also weaken your immune system over time—even in childhood.

How Can You Strengthen Your Immune System?

Just because your immunity is not something you can entirely control doesn't mean you should throw caution to the wind and start abandoning your healthy habits—quite the opposite, really.

Start with a look at your diet: Nutrients from fruits and veggies, like zinc, iron, and vitamin C, are essential for a healthy immune system, Dr. Phillips said, as are omega-3 fatty acids. "Omega-3s found in fatty fish, like salmon, also encourage the production of lymphocytes—immune cells that are the front line of defense against infections," she explained. And it's better to get your immune-protective nutrients through food than through supplements, Dr. Phillips added.

Getting plenty of sleep and exercise also helps boost your immune system—whether it feels like these healthy habits are working in your favor or not. Exercise improves circulation; increased circulation boosts the production of germ-fighting antibodies, Dr. Phillips explained. "Exercise also lessens stress, which helps your immune system function at its best," Dr. Phillips added.

Sleep is a health-restorative time for the body. "When you sleep, your body releases immune proteins called cytokines, which help fight infections and control the body's response to stress," Dr. Phillips said. "So a lack of sleep can lead to an under-production of cytokines and other protective immune cells, leaving you more vulnerable to infection."

Your best bet (and mine too, apparently): Stick to the healthy habits you already have in place, and maybe add a few more. But keep in mind that just because you seem to get sick so often, it doesn't necessarily mean you're unhealthy—you're just a bit more susceptible to coming down with something.

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