Men may actually experience worse symptoms when they catch a cold or flu. What looks like exaggeration has a biological basis: testosterone suppresses immune function, while estrogen strengthens it, meaning male bodies often mount a weaker defense against common respiratory viruses. That doesn’t explain the whole picture, but it does mean “man flu” is more than just a personality flaw.
Testosterone Weakens the Immune Response
The core of this story is hormonal. Estrogen, the primary sex hormone in women, helps regulate the immune system’s inflammatory signals and boosts the production of interferons, proteins that are critical for fighting off viral infections. Estrogen essentially fine-tunes the immune response, making it more effective without letting it spiral out of control.
Testosterone does roughly the opposite. A study published in the Proceedings of the National Academy of Sciences found that men with the highest testosterone levels produced the lowest antibody responses after receiving a flu vaccine. In that study, 33 women but only 10 men mounted a strong antibody response to one flu strain, while 24 men were non-responders compared to 20 women. The pattern was clear: the more testosterone in a man’s system, the weaker his immune defense. This isn’t a small or subtle effect. Men in the highest testosterone group were roughly five times less likely to respond well to the vaccine than men with lower levels.
This trade-off may be evolutionary. The immunocompetence handicap hypothesis, a well-known concept in biology, suggests that testosterone-fueled traits like muscle mass and competitive behavior come at a real cost to the immune system. In other words, the hormones that make male bodies physically stronger also leave them more vulnerable to infection.
Men Get Sicker Faster
It’s not just that men’s immune systems are weaker on paper. Research on influenza infection shows that male bodies ramp up certain inflammatory chemicals faster than female bodies do, which translates to more severe symptoms hitting sooner. In one study, males produced a faster spike in interleukin-1β, a key driver of fever, fatigue, and appetite loss. That faster inflammatory burst came with more pronounced behavioral symptoms: infected males lost their appetite earlier and showed more dramatic drops in activity compared to females.
Separate lab work backs this up. When researchers isolated immune cells from 63 healthy people and exposed them to rhinovirus (the common cold virus), cells from premenopausal women mounted a stronger immune response than cells from men of the same age. A stronger initial immune response means the body clears the virus more efficiently, which typically means a shorter, less miserable illness.
A 2017 review in the British Medical Journal pulled this evidence together and concluded that “men may not be exaggerating symptoms but have weaker immune responses to viral respiratory viruses, leading to greater morbidity and mortality than seen in women.” The author, Kyle Sue, a clinical professor in Canada, argued that dismissing men’s complaints as drama is “potentially unjust” given the biology involved.
But Biology Isn’t the Whole Story
Hormones create a real difference in how hard a virus hits, but they don’t fully explain why some men seem to collapse on the couch while running a low-grade fever. Social and psychological factors play a role too, and they’re more nuanced than “men are babies.”
Research on illness behavior shows that women are actually more likely to notice and report symptoms in general. Women tend to monitor their health more closely, recognize early signs of illness sooner, and seek medical care faster. Men, by contrast, often ignore symptoms until they become impossible to push through. So when a man finally acknowledges he’s sick, he may genuinely be at a worse point in the illness than a woman who recognized and started managing her symptoms earlier.
There’s also the question of practice. Many women are socialized to keep functioning through discomfort, whether that’s menstrual pain, pregnancy symptoms, or simply the expectation that household responsibilities don’t pause for a cold. Men are less likely to have built up that same routine of powering through physical misery, so when illness hits, the disruption feels more dramatic to everyone around them.
Hospitalization Rates Tell a Mixed Story
If men truly get hit harder by respiratory viruses, you might expect them to be hospitalized more often. CDC surveillance data from 2010 through 2023 shows a more complicated picture. In the 2022-23 flu season, women were actually hospitalized at a higher rate (69.4 per 100,000) than men (59.2 per 100,000). But hospitalization rates reflect who seeks care, not just who is sickest. Women’s higher rates of health-seeking behavior likely push that number up, while men’s tendency to avoid hospitals unless absolutely necessary pulls theirs down.
Mortality data, which can’t be skewed by care-seeking behavior, has historically shown men dying from flu and pneumonia at higher rates than women. That aligns with the immune suppression story: men’s bodies are less equipped to fight off severe respiratory infections, even if they’re less likely to show up at a hospital for moderate ones.
What This Actually Means
The “man flu” is real in the sense that male biology creates a genuinely worse experience with common viruses. Testosterone suppresses immune function, men’s inflammatory responses hit harder and faster, and their bodies are less efficient at clearing infections. None of that is exaggeration. It is, however, also true that social conditioning shapes how people express discomfort, and men who rarely deal with ongoing physical symptoms may have less experience managing illness gracefully.
Both things can be true at once. The guy on the couch moaning about his cold probably does feel worse than you would with the same virus. He may also be less practiced at functioning through it. Understanding the biology doesn’t require dismissing the behavior, but it does suggest a little more sympathy might be warranted.