What Causes a Common Cold to be Severe? 8 Reasons it Hits Some People Harder

The common cold is certainly common. The roughly 350 million residents of the U.S. suffer about 1 billion colds annually, with colds being most prevalent among children. If you do the math, this means a typical person catches a cold three times per year.

Given that reality, it’s no surprise that the common cold is the most common infectious disease in the U.S. In fact, it’s responsible for the most visits to doctors’ offices and the most school and work absences.

Of course, some people come down with a nasty cold more often than others in a year’s time while other people experience mild symptoms (or escape a cold altogether). But why is that?

What causes a common cold to be severe?

The main culprit: How quickly and effectively your immune system reacts when exposure first happens. All of the other factors — genetics, exposure, age and health habits — shape that response.

Here are the eight key factors that determine whether a cold causes you to frequently cough, sniffle and sneeze.

1. Immune system response

It’s not the power of cold viruses, often rhinoviruses, but the body’s response to them that dictates the severity of a cold, according to a study published in 2026 by the journal Cell Press Blue. The study emphasized the major role played by the reaction of cells that form the lining of nasal passages, Yale News explained.

“These cells have an arsenal of innate defense mechanisms triggered by viruses (also called ‘innate immunity’), even though they are not part of the traditional immune system,” according to Yale News. “[Researchers at Yale] identified a switch that determines whether a rhinovirus infection remains a mild cold or escalates into the kind of severe airway inflammation that can land someone in the emergency room.”

The body’s first-line antiviral defense in the nose — called the interferon response — typically keeps the rhinovirus in check, Yale News says. When the response works properly, fewer than 2% of nasal cells become infected with rhinovirus and the cold fizzles.

Researchers found that most cold infections remain mild because the nasal lining rapidly generates interferons that prevent the virus from spreading to other cells, according to Yale News.

“But when that response is weakened or blocked, the body reacts with a more aggressive inflammatory mode that can worsen symptoms and damage airways,” according to Yale News.

2. Genetics

Genetics also contributes to whether you catch a cold. According to Scientific American, some people are born with a genetic predisposition toward easily becoming infected. Meanwhile, other people might possess genetic characteristics that offer extra protection from infections, according to Henry Ford Health.

3. Previous exposure

An article published by the journal Frontiers in Allergy explains that adults come down with fewer colds than children because they’ve had more exposure to cold viruses. Infants contract six to eight colds a year, compared with two to four per year among adults.

On top of that, people with less previous exposure might experience colds with more serious symptoms. Also, people who’ve gone awhile without catching a cold might suffer worse symptoms when they do get sick.

4. Amount of viral exposure

A study published in 2018 by the journal Clinical Infectious Diseases found that a larger “viral load,” or higher initial exposure to a cold virus, can cause worse cold symptoms. That’s because your immune system must fight harder to attack a larger viral load. And that larger viral load can increase nasal inflammation, which is tied to worse cold symptoms.

5. Age

As we age, the ability of our immune system to ward off infections decreases, particularly if you’re 65 or older.

“Even a seemingly mild cold can pose a health threat to older adults. It can lead to pneumonia, an acute illness that takes the lives of thousands of people in the U.S. each year,” the National Council on Aging says. “Additionally, if you have a chronic condition such as asthma, COPD or emphysema, a cold can intensify the symptoms from those conditions for several weeks after your cold symptoms have resolved.”

6. Gender

Research shows women come down with more colds than men do, possibly because they typically spend more time around virus-carrying children. However, women’s immune systems generally are stronger than men’s. Why? Because research suggests the female hormone estrogen strengthens the immune system, while the male hormone testosterone weakens immune responses.

7. Health

Factors such as poor nutrition, chronic illness, high stress levels and cigarette smoking can drain your immune system, leaving you more susceptible to a nasty cold than a healthier person.

Also, a lack of regular exercise might open the door to a cold virus, while 30 to 45 minutes of moderate-intensity exercise four to five days a week can help prevent a cold, according to the University of Wisconsin-Stout.

In addition, people who are underweight or overweight, because of their insufficient metabolic health, might suffer more severe cold systems due to depleted immunity.

8. Sleep

A study published in 2010 by the Archives of Internal Medicine found that poor sleep efficiency and short sleep duration before exposure to a cold virus resulted in less resistance to a cold. In fact, people who slept less than seven hours per day were nearly three times more likely to come down with a cold than people who slept at least eight hours, the study showed. Furthermore, sleep deprivation can worsen cold symptoms because of weakened immune response.