Why Do I Keep Getting Sick? The Real Reasons — and the Ones That Are Myths

You've had three colds this winter and you've reached the obvious conclusion: your immune system is weak. It's the wrong frame, and letting go of it is the most useful thing you can do. For most healthy adults, a run of colds isn't a broken immune system. It's a handful of everyday factors that genuinely move the needle — plus a lot of folklore that doesn't. Here's which is which.

The reframe that changes everything

Start here, because it reshapes the whole question. You can't "boost" a normal immune system into overdrive — and you wouldn't want to. An immune system running hotter than it needs to is how you get allergies and autoimmune trouble, not superhuman resistance. The goal was never a supercharged immune system. It's a well-functioning one.

That's not a technicality. It's why the aisle full of products promising to "boost" your immunity is selling something you don't want and can't actually buy. What you can do is stop undermining the system you've got. That's where the real drivers come in.

What genuinely makes you more susceptible

Three things have real experimental evidence behind them — not association, but studies where people were deliberately exposed to a virus and tracked.

Too little sleep. This is the big one. In one study, people were exposed to a cold virus under controlled conditions, and those sleeping six hours or less a night were around four times more likely to actually come down with a cold than those sleeping more than seven. Not a bit more likely. Four times. Sleep isn't the soft option among immune factors — on this evidence, it's the hardest-hitting one.

Sustained stress. Not a bad afternoon — prolonged psychological stress, the kind that runs for weeks. A classic study found infection risk rose steadily the more stress people were under: a clear dose-response, holding across several different viruses. The longer the pressure, the higher the susceptibility.

Too much hard training. Exercise cuts both ways here. Moderate, regular activity is protective — people hitting roughly the standard activity guidelines get noticeably fewer respiratory infections. But repeated heavy, prolonged exertion — think marathon training, not a gym session — is associated with more infections in the following week or two. The traditional explanation for that second effect is now genuinely debated among researchers; what's not debated is the protective side of moderate exercise. [Internal link: the exercise-immunity piece]

What actually defends you — and it's boring

The two most effective defences aren't exciting, which is probably why they're undersold.

Washing your hands. Unglamorous and genuinely effective. Pooled trial evidence puts hand hygiene at roughly a 14% reduction in respiratory illness. No supplement in this piece beats that.

Vitamin D — but only if you're actually short of it. This is the honest version of a claim that usually gets oversold. Across the trial evidence, vitamin D modestly reduced respiratory infections — but the benefit was concentrated in people who were genuinely deficient to begin with, and from steady daily or weekly doses, not occasional big ones. For someone already replete, it did little. It's a correction for a real shortfall, not a general shield.

That shortfall is common in a British winter, which is why the NHS advises that "everyone should consider taking a daily supplement containing 10 micrograms of vitamin D during the autumn and winter" — when we can't make enough from sunlight. Note the logic: that's about correcting a widespread seasonal deficiency, not boosting anyone above normal.

The myths worth dropping

"I went out with wet hair and caught a cold." Being cold doesn't give you a cold. You need the virus — no virus, no cold, however chilled you get. Colds are commoner in winter mainly because we crowd indoors together and spread them more easily. There's a plausible idea that a cold nose may weaken local defences slightly, but that's an emerging line of research, not settled fact — so the wet-hair story remains, at best, a bit-part player and not the cause.

"I need to boost my immune system." Covered above, but it's the myth under all the others. There's no boosting a healthy system into a better one. There's only supporting normal function — and not sabotaging it with no sleep and months of stress.

When it's worth seeing a GP

One honest caveat. If your infections are genuinely frequent, unusually severe, or slow to clear in a way that's out of step with the people around you, that's worth a GP conversation — occasionally it points to something underlying. For the ordinary run of winter colds, though, the answer usually isn't a weak immune system or a missing supplement. It's sleep, stress, and the basics.

Disclaimer: The content above is for educational and informational purposes only. It is not medical or nutritional advice, and nothing herein should be taken as a recommendation to use, purchase, or rely on any specific supplement or ingredient. Always consult a qualified healthcare professional before making changes to your diet, supplement routine, or health practices. We make no guarantees about the accuracy or completeness of the information provided. Any actions you take based on this content are at your own risk.