The common cold: what really shortens it, and what does nothing

Resfriado: lo que de verdad acorta los días y lo que no hace nada

Illustrative image. Does not represent guaranteed results.

What your body is already doing right

Let's start with what almost nobody says when you wake up with a blocked nose: your body knows how to do this. It has done it dozens of times and it will do it again. In a few days you will be fine, and it won't be because of what you bought at the pharmacy.

That doesn't leave you with nothing to do. The opposite. Your job during a cold isn't to kill the virus — your immune system handles that, and it's good at it — it's to give that system the conditions to work fast and to get through the days as comfortably as possible. And there are real decisions that change the count.

The interesting part is which ones. What moves the number isn't in the cough-syrup aisle: it's how many hours you slept last week, whether you move, and a glass of salt water. This article goes in that order: first what works, then what relieves, then what does nothing, and at the end the signs that genuinely mean someone should look at you.

What a cold actually is

A cold is a viral infection of the nose and throat. It isn't one disease with one culprit: more than two hundred different viruses can cause it, and the most common are rhinoviruses. That's why there is no cold vaccine, and why you catch colds again: it isn't that your defenses failed, it's that you met a different virus you had no memory of.

What you feel — blocked nose, mucus, scratchy throat, cough, fatigue — is largely your own immune response, not damage from the virus. Your nose swells because that's where your defense cells arrived. Mucus is part of the cleaning system. And one detail worth gold: green or yellow mucus does not mean this is bacterial or that you need an antibiotic. The color comes from an enzyme in your own white blood cells; it's a sign your defenses are working.

The strongest tool is free: sleep

If you take one thing from this article, take this.

In 2015, a team from the University of California, San Francisco and Carnegie Mellon ran a study you can hardly run on other topics: they measured first and exposed afterward. They put a wrist monitor on 164 healthy adults for seven nights, to measure how much they actually slept rather than how much they thought they slept. Then they quarantined them, put rhinovirus drops — the cold virus, on purpose — in their noses, and watched them for five days.

Among those sleeping more than seven hours, plenty met the virus without getting sick. Among those sleeping under six hours, the odds of ending up with a real cold were roughly four times higher — even after accounting for age, weight, season, stress, pre-existing antibodies and health habits.

Notice what this means: it isn't that short sleep gives you a cold, it's that it changes what happens when you meet the virus. Two people in the same house, with the same virus in the air, do not carry the same risk. It's 164 people and the confidence intervals are wide, so the exact figure isn't a law — but the direction has held up since.

If colds are going around the office or the school this week, what time you go to bed is a medical decision. And if you're already sick, sleep is still the work — not "resting" in the abstract, sleeping. That's the part of the treatment nobody sells. The full picture is in sleep and longevity.

Moving: 43% fewer sick days

The second tool is also free. One study followed 1,002 adults aged 18 to 85 across twelve weeks of fall and winter, logging their symptoms daily with a validated questionnaire, and compared those doing aerobic exercise five or more days a week against those who barely moved.

The first group spent 43% fewer days with symptoms. And when they did get sick, symptoms were 32% to 41% less severe. Comparing by fitness level instead of frequency, the gap was 46%.

What kind of study this is, stated plainly: nobody here was randomly assigned to exercise. People who already moved were compared with people who didn't, adjusting for seven potential confounders. The association is solid, but it doesn't prove causation on its own — someone who trains five days a week probably also sleeps better. That said, a brisk half-hour walk has no downside, and the detail is in VO2 max and longevity.

A note for when you're already sick: this is prevention, not treatment. The practical rule: if symptoms are from the neck up and you feel able, easy movement is fine; with fever or chest symptoms, no.

Salt water: the most interesting finding in colds

This one surprises people, and we're going to tell it in full — the good part and the uncomfortable part — because both are true.

In Edinburgh, a team at the Royal Infirmary started from something visible in the lab: the cells lining your nose and throat use chloride — half of table salt — to make a substance that gets in the way of viruses. The question was whether raising it locally would do anything in real life.

They recruited 68 adults within 48 hours of a cold starting. Half carried on with usual care; half learned to make the solution at home and use it in the nose and as a gargle. The salt-water group had colds 1.9 days shorter, used 36% fewer over-the-counter medicines, shed less virus, and — the part that matters most in a household — passed it on to the people they lived with 35% less often.

Now the honest part, and it's substantial. That study was a pilot: 68 people, unblinded — everyone knew which group they were in — and its stated primary outcome was whether participants could be recruited at all, not whether the treatment works. The authors say so outright: a larger trial is needed. And the same investigator later tested the same technique in 576 people with COVID, and it did not work: no difference versus control. A negative result, published by the very team that championed the idea. That's science working properly, and it's why we are not going to tell you that salt water "shortens a cold by two days."

So do you do it or not? It's salt water. It costs nothing, carries no risk when prepared properly, clears a blocked nose even if only mechanically, and has one small trial in its favor. On those terms, trying it is reasonable. Two rules: use boiled-and-cooled, distilled or sterile water — never straight tap water — and don't share the device.

What helps while it passes

Honey, for cough

Honey is not an unsupported folk remedy: it's one of the best-studied things available for cough in children. A Cochrane review pooled six trials with 899 children aged one to eighteen and found it reduces cough frequency better than no treatment and better than placebo, with moderate certainty. Against dextromethorphan — the classic cough syrup — it came out roughly even.

Two limits. In most of those trials honey was given for a single night, so what's proven is short-term relief, not a shorter illness. And the second is not negotiable: never honey before the first year of life, because of infant botulism. No exceptions.

Zinc, with asterisks

Zinc is the opposite case: a lot of noise and messy evidence. The most-cited review pooled 17 trials with 2,121 people and found oral zinc shortened colds by an average of 1.65 days, with more effect in adults than children.

But that average hides a problem. Variability between the trials was enormous — reported as I² of 95%, which in practice means they aren't measuring the same thing — and it didn't resolve when split by dose, age or zinc salt. With results that scattered, the average is fragile. It also has a cost: the zinc group reported more bad taste and nausea than placebo, and the authors themselves ask for large trials before any firm recommendation.

Our reading, unvarnished: it may help some adults a little if started very early, the effect is far from clear, and in exchange there's a decent chance of bad taste and nausea. It is not the centerpiece of anything, and don't invent your own dose.

What helps and needs no study

• Fluids. Not because they "flush" anything, but because fever and mouth-breathing dehydrate you, and that makes you feel worse than you are.
• Humid air. A steamy shower or a clean humidifier eases nose and throat while it lasts.
• Plain saline in the nose, drops or spray. It clears, has no side effects, and is safe even in babies.
• Acetaminophen or ibuprofen for headache, body aches and fever, at label doses. They don't shorten the cold; they make the days easier to carry, and that's reason enough.
• Washing your hands. The most boring measure and one of the most effective for not passing it on: the virus travels on hands and surfaces, not just in the air.

What doesn't work and still costs you money

The pill decongestant: the FDA wants it gone

This is the one that saves a family the most money, and almost nobody knows it.

Look at the box of your cold medicine. If the active ingredients list phenylephrine and it's something you swallow — tablet, capsule or syrup — the FDA concluded that at those doses it does not work as a decongestant. In November 2024 the agency issued a proposed order to remove oral phenylephrine from the list of ingredients approved for over-the-counter use, after reviewing the studies and finding that what you swallow is broken down in the liver before it ever reaches your nose.

Three clarifications so this is actually useful:

• It is a proposed order, not a final one. The comment period closed in May 2025 and the final decision is still pending. Until then these products can legally stay on sale, which is why you still see them on the shelf.
• The FDA did not say it is dangerous. It said it does not work. This is an efficacy issue, not a safety one.
• This applies only to phenylephrine taken by mouth. Decongestant nasal sprays are a different matter and do work — they go straight where they're needed — though they shouldn't be used more than three days in a row, to avoid rebound congestion.

Put the most useful way: if you buy a box for congestion and the only decongestant in it is oral phenylephrine, you are paying for the part that doesn't do the job. What's helping you, if anything is, is the pain reliever or the antihistamine riding along with it.

Antibiotics

An antibiotic does nothing to a virus. Almost everyone knows that in theory, and colds are still one of the leading reasons antibiotics get prescribed unnecessarily.

The Cochrane review of antibiotics for the common cold, updated in 2025, pooled six trials with 1,147 people: no benefit. People who got an antibiotic did not recover sooner or have fewer persisting symptoms than those on placebo. What there was, was more harm: the risk of adverse effects was close to double, and in adults more than double. That same review looked at thick, colored mucus specifically, and found no benefit there either.

A clinician telling you "this is viral, you don't need an antibiotic" is not denying you something. It's the right answer, and the one that protects you from the side effects of a drug that wasn't going to help.

And vitamin C

Taking it once the cold has already started generally changes nothing measurable. The small benefit that shows up in the evidence belongs to people taking it daily before getting sick, and we're talking hours off days. If you like taking it, it does no harm — but it isn't the missing piece.

Children are not small adults

They get far more colds, and that's normal. An adult gets two or three a year; a small child can get six to eight, or more in daycare. That isn't a weak immune system: it's a new one, meeting viruses one at a time. The number drops with age on its own.

Cough and cold medicines are not for them. They aren't recommended under age four, and from four to six only on a clinician's advice: the benefit isn't established at that age and the adverse effects are. What does have support is saline in the nose, fluids, and honey after the first year.

The threshold for calling is lower. In a baby under three months, any fever is a call today, not a wait. And at any age, a child who is struggling to breathe, won't take fluids, or is unusually drowsy or irritable needs to be seen in person.

The signs that don't wait

Most colds need nobody. These situations do — not to frighten you, but so you know what you're watching for while it passes.

Call 911 or go to the emergency room if there is:

• Difficulty breathing, shortness of breath at rest, or fast, labored breathing.
• Chest pain or pressure.
• Blue or gray lips or face.
• Confusion, inability to wake the person properly, or a sudden change in how they are.
• A stiff neck with fever and severe headache, or inability to tolerate light.
• In a baby: not being able to breathe and feed at the same time, or the ribs pulling in with each breath.

Be seen today, even if it isn't an emergency, if there is:

• You got better and then got worse. This is the most important pattern on the list: it's usually what signals a bacterial complication on top of the virus, such as sinusitis or an ear infection.
• Fever that returns after going away, or fever lasting more than three or four days.
• More than ten days with no improvement at all, not just a lingering cough.
• Ear pain, severe face or tooth pain, or pain over a sinus.
• Wheezing, or asthma that's getting away from you.
• Not being able to keep fluids down, or signs of dehydration.
• Fever in someone who is pregnant, a frail older adult, or anyone immunocompromised.

And a reminder worth repeating: when the question is breathing, you don't search the internet. You call 911.

The video visit: what it does and doesn't do

We put this here, in the middle rather than buried at the end, because if you're going to use it we want you to know exactly what you're buying.

SCTS1 offers a $59.99 video visit with a licensed provider, in English or Spanish, for the usual reasons: colds, sore throat, eczema, acne, rashes and several more.

What a video visit does resolve

• A licensed provider listens: how many days, how it started, whether there was fever, who else is sick at home, what you take and what your history is.
• Separates what looks like a common cold from what might be something else — flu, COVID, sinusitis, an ear infection, asthma getting away from you — which is exactly what you can't decide by reading a list.
• Tells you whether a test makes sense and where to get it.
• Prescribes if the case calls for it, and explains why if it doesn't.
• Reviews what you're already taking: different boxes with the same ingredient doubled up, or a decongestant that doesn't suit your blood pressure.
• Makes clear what signs to watch for and when to stop waiting, and handles the dull but real part: the work or school note.

What it does not

• Nobody can listen to your lungs through a screen, or look inside your ear. If the decision needs that, the visit tells you so; it doesn't do it.
• No samples are taken and no tests are run by camera.
• It is not the place for an emergency. Nothing on the list above is handled by video.
• It is not the place to get an antibiotic just because. If the case is viral, the honest answer will be no.

The order, no fine print: the visit costs $59.99 and you start it. Then a licensed provider reviews your case and decides what's appropriate, including whether a test or a medication is needed. Eligibility is determined by medical evaluation. The visit has a price, and we don't promise an outcome.

Licensed provider, in English or Spanish. If this is an emergency, call 911.

So your expectations are the right ones

One. A cough lasts longer than you think, and that's normal. There's a study that deserves to be famous: 493 adults were asked how long they expected a cold cough to last, and answered seven to nine days; then the literature was reviewed for how long it actually lasts without treatment, and the average was 17.8 days. That gap is one of the reasons so many people go asking for an antibiotic on day ten — not because something is wrong, but because they thought they should already be well.

Two. Blocked nose and mucus usually peak on day two or three and then ease. Being worse on Tuesday than you were on Monday doesn't mean something is wrong: it means your immune response is at its peak.

Three. Nothing in this article cures a cold. The best the evidence offers is a few days fewer, more bearable symptoms, and less transmission at home. That's real and it's worth having; anyone promising to take the cold away is selling you something. And the figures here are averages from the populations studied, not a forecast for you: individual results vary and are not guaranteed.

Who is this NOT for?

This section is not negotiable, and we write it in full even though it doesn't sell.

The video visit is not for you if:

• You have any of the emergency signs listed above. That's 911 or in-person care now, not a camera.
• The patient is a baby under three months with a fever. That's an in-person evaluation the same day.
• You have difficulty breathing or wheezing, or asthma or COPD getting away from you with the cold. Lungs have to be listened to.
• You are on chemotherapy, taking immunosuppressants, have had your spleen removed, or have a condition that lowers your defenses. Your threshold for in-person care is much lower than everyone else's, and your primary physician needs to be in the conversation.
• You are pregnant and have a fever: that call goes to whoever is managing your pregnancy.
• What you want is an antibiotic without an evaluation. This isn't that, and we won't pretend otherwise.
• You've had more than ten days of the same or worse: that is no longer managed as a cold.

Frequently asked questions

How long does a cold last?

Blocked nose and feeling unwell usually run a week to ten days, peaking on day two or three. The cough is what lingers: its real average duration in the medical literature is 17.8 days, well beyond the seven to nine people expect. A cough slowly improving at day twelve is normal. What isn't normal is getting better and then getting worse.

What shortens a cold the most?

Of what's been measured in people, the strongest things are sleep — in a virus-exposure study, sleeping under six hours made people about four times more likely to get sick — and regular movement, associated with 43% fewer days of symptoms. Once it's started, the most interesting signal is salt-water nasal irrigation and gargling in the first 48 hours: 1.9 days shorter in a pilot trial.

Does the pill decongestant work?

If the active ingredient is phenylephrine and you swallow it, the FDA concluded it does not work as a decongestant at those doses, and in November 2024 proposed removing it from the ingredients approved without a prescription. This is about efficacy, not safety, and the final decision is still pending, so it's still sold. Nasal sprays are a different matter and do work, but not more than three days in a row.

The mucus is green. Do I need an antibiotic?

No. The color comes from an enzyme in your own white blood cells and signals that your defenses are working, not a bacterial infection. The 2025 Cochrane review looked specifically at thick, colored mucus and found no benefit from antibiotics, but did find more adverse effects.

Is zinc worth it?

It's doubtful. The main review found 1.65 days shorter on average, but with so much variability between trials that the average is fragile, and with more bad taste and nausea than placebo. It may help some adults a little if started very early. It is not the centerpiece of anything.

What does the $59.99 visit include?

The evaluation with a licensed provider, in English or Spanish, by video: your history, separating a common cold from something else, guidance on whether a test is needed, a prescription if appropriate, a review of what you're already taking, the signs to watch for, and the work or school note. Eligibility is determined by medical evaluation. If this is an emergency, call 911.

Sources

• Prather AA, Janicki-Deverts D, Hall MH, Cohen S. Behaviorally assessed sleep and susceptibility to the common cold. Sleep. 2015;38(9):1353-9. — DOI
• Nieman DC, Henson DA, Austin MD, Sha W. Upper respiratory tract infection is reduced in physically fit and active adults. Br J Sports Med. 2011;45(12):987-92. — DOI
• Ramalingam S, Graham C, Dove J, Morrice L, Sheikh A. A pilot, open labelled, randomised controlled trial of hypertonic saline nasal irrigation and gargling for the common cold. Sci Rep. 2019;9(1):1015. — DOI
• Yusuf OM, Ramalingam S, Norrie J, et al. Hypertonic saline nasal irrigation and gargling for suspected or confirmed COVID-19: pragmatic randomised controlled trial (ELVIS COVID-19). J Glob Health. 2024;14:05027. — DOI
• Science M, Johnstone J, Roth DE, Guyatt G, Loeb M. Zinc for the treatment of the common cold: a systematic review and meta-analysis of randomized controlled trials. CMAJ. 2012;184(10):E551-61. — DOI
• Oduwole O, Udoh EE, Oyo-Ita A, Meremikwu MM. Honey for acute cough in children. Cochrane Database Syst Rev. 2018;4(4):CD007094. — DOI
• Kenealy T, Arroll B. Antibiotics for the common cold and acute purulent rhinitis. Cochrane Database Syst Rev. 2025;11(11):CD000247. — DOI
• Ebell MH, Lundgren J, Youngpairoj S. How long does a cough last? Comparing patients' expectations with data from a systematic review of the literature. Ann Fam Med. 2013;11(1):5-13. — DOI
• U.S. Food and Drug Administration. Proposed order: amending over-the-counter monograph M012 — oral phenylephrine as a nasal decongestant (OTC000036). November 2024. — FDA

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This article is informational and is not medical advice, and does not replace an in-person evaluation. SCTS1 does not prescribe or dispense medication: all medical care, prescriptions and treatment plans are provided by licensed providers through our partner platform, and eligibility is determined by a licensed provider through medical evaluation. The figures cited are averages from studied populations and are not a forecast for your case; individual results vary and are not guaranteed. A video visit does not replace emergency care: if you have difficulty breathing, chest pain, confusion or a stiff neck, call 911.