How long is a cold contagious?

You can start spreading it from a few days before symptoms begin. The CDC puts the illness itself at usually less than a week.

That makes a cold the most casually shared illness on this site. Nobody isolates for a cold, and no European authority asks them to. But the NHS window is longer than most people assume, and the question that matters is rarely whether you can go to work: it is whether you can hold a newborn or visit a grandparent. The NHS is the main source here and the CDC fills in where the NHS is silent, at each point by name.

Day by day

Counting the day symptoms start as day 0, this is how the UK & USA (NHS / CDC) figures fall.

Are you contagious before cold symptoms start?

Yes, but the NHS gives no number. A person with a cold can start spreading it from a few days before their symptoms begin, in its words, and that is as precise as it gets, so this page gives no number of days either.

The timeline is short in any case. The CDC says the signs and symptoms of a cold usually peak within two to three days of infection, and the NHS says symptoms come on gradually over two to three days, so the gap between catching a cold and having one is a matter of days. Italy's ISS gives an incubation of two to three days; the NHS and the CDC publish none.

When is a cold most contagious?

Neither the NHS nor the CDC names a most-contagious day for a cold. What they describe is the shape of the illness: symptoms build over two to three days, the NHS says, and peak within two to three days of infection, the CDC says. The days of heaviest sneezing and the runniest nose are the days you spread most virus, by the route the NHS describes: coughs and sneezes.

Colds are spread by germs from coughs and sneezes, which can live on hands and surfaces for 24 hours, according to the NHS. The CDC adds that more than 200 respiratory viruses can cause colds, rhinoviruses most often, and that adults average two to three colds a year and children more. That variety is one reason no authority publishes a day-by-day contagious curve: there is no single cold virus to measure.

How long does a cold last, and when does it stop being contagious?

The NHS gives both answers in one sentence: you are infectious until all your symptoms have gone, which usually takes one to two weeks, and longer in babies and young children. The CDC's figure for the illness is shorter, usually less than a week. Both are describing the same thing, a range from a few days to a fortnight, with the NHS taking the cautious end.

The cough is where readers want an exception, and the NHS does not give one. Its wording is 'all your symptoms', and it asks you to see a GP if a cough lasts more than three weeks, which tells you coughs can run that long. Germany's gesund.bund.de says the same, up to three weeks. What the CDC adds, for respiratory viruses in general, is that you are likely to be less contagious once your symptoms have fully cleared, and that after its 24-hour threshold it asks for five days of precautions rather than none.

So the honest reading is this: the NHS says a cold is contagious while any symptom remains; no UK authority says a lone cough is safe; and the CDC's general guidance is that contagiousness fades as symptoms clear rather than switching off. Around a newborn or a frail relative, treat the cough as a symptom.

Is there a test for a cold?

No. The NHS cold page does not mention testing, and the CDC's public testing page describes home tests for COVID-19 and flu, not for the 200-plus viruses behind colds. A negative COVID-19 or flu test tells you what you do not have; it does not name the cold virus and it does not change how long you are contagious. The CDC says testing does not change how likely you are to catch or spread a respiratory virus.

The exception is when a cold might be something else. A sudden high temperature and body aches point to flu, and cold symptoms in a baby under six months or an adult over 75 raise the question of RSV, for which the NHS lists both groups as at higher risk. In those cases a doctor may test to decide on treatment, not to decide when you can go out.

Treatment: nothing shortens the contagious period

GPs do not recommend antibiotics for colds because they will not relieve your symptoms or speed up your recovery, the NHS says; antibiotics only work if you have a bacterial infection, and colds are caused by viruses. There is no antiviral for the common cold on any NHS or CDC page used here, and nothing either authority describes shortens the time you are contagious.

That leaves symptom relief and time. The NHS timeline runs from first symptom to last, and no medicine moves the finish line. What the CDC watches instead is the fever: 24 hours without one and without fever-reducing medicine, with symptoms improving, is its threshold for going back to normal activities.

Should you stay at home with a cold? Work, school and nursery

The NHS does not ask you to stay at home for a cold as such. Its rule is conditional: if you have a high temperature or do not feel well enough to do your normal activities, try to stay at home and avoid contact with other people until you feel better. For nurseries and schools, the UK Health Security Agency's exclusion list says the same for any respiratory infection: a child stays away if they have more than mild symptoms, for example a high temperature. A child with a runny nose and no fever can go in.

The CDC's threshold is 24 hours of improving symptoms with no fever and no fever-reducing medicine, followed by five days of precautions such as a well-fitting mask and distance. Germany's BZgA is the strictest neighbour: three to five days at home and until symptoms have improved, for any respiratory infection. Spain's Catalan health service says the opposite, that a mild respiratory infection generally does not require a child to stay at home. France's Ameli, Italy's ISS and the Dutch Thuisarts publish no rule; they say how long symptoms last instead: five to twenty days, seven to fourteen days and a couple of weeks respectively.

Everyday situations: a newborn, grandparents, a shared bed, the gym, a flight

Count from the first day of symptoms, and remember the NHS window runs until the last symptom has gone.

• A newborn in the house: the NHS says keep newborn babies away from anyone with a cold or the flu, on both its RSV and its bronchiolitis pages, because a winter cold in an adult may be RSV and babies under six months are at highest risk. Wash your hands before every contact, and keep a sneezing sibling out of the baby's room until the symptoms have gone.
• Grandparents: adults over 75 are on the NHS higher-risk list for RSV, which looks like a cold. Put the visit off until your symptoms have gone, which is where the NHS ends the contagious period, or at the very least until you have passed the CDC's 24-hour threshold and its five days of precautions.
• Sharing a bed: colds spread by coughs and sneezes, and the germs survive 24 hours on hands and surfaces, according to the NHS. Separate rooms for the worst two or three days are worth it if the other person is pregnant, older or immunosuppressed; otherwise the NHS asks nothing of you.
• The gym: if you do not feel well enough for your normal activities, the NHS says stay at home; if you do, it places no restriction. Wipe down equipment: those germs live on surfaces for 24 hours.
• A flight or a family dinner: no NHS or CDC rule mentions travel. Apply the CDC's 24-hour threshold and its five days of precautions, and skip a dinner with a newborn or someone over 75 until your symptoms have gone.
• A care-home visit: the NHS cold page sets no visitor rule, but care-home residents are offered the RSV vaccine because they are at risk from exactly the viruses a cold can be. Wait until your symptoms have gone.

How long is a cold contagious in children, older adults and people with weakened immunity?

Children are the group the NHS singles out. It says a cold can last longer in young children and that the infectious period can be longer in babies and young children, but it gives no number, and neither does the CDC, which says only that children have more colds than adults. No European authority in this comparison puts a figure on it for colds either.

On weakened immunity, the NHS cold page says nothing. The CDC's general respiratory-virus guidance says people with immunocompromising conditions can shed a virus for a long time, without a number. No authority says older adults stay contagious for longer; they are the people a cold can harm, which is why the NHS lists a long-term condition or a weakened immune system among the reasons to see a GP about a cold, alongside a cough lasting more than three weeks and symptoms not better after ten days.

Why the official guidance on colds differs between countries

The differences here are mostly about what each authority chose to measure. The NHS measures contagiousness and ties it to symptoms: until all of them have gone, one to two weeks. The CDC measures the illness: usually less than a week. Ameli, the ISS and Thuisarts measure symptom duration too, and get five to twenty days, seven to fourteen days and a couple of weeks. Germany publishes a return rule, three to five days, without publishing a contagious window at all. Spain publishes a school rule, no exclusion for mild cases, and nothing else.

Underneath lies a fact the CDC states and the others assume: a cold is more than 200 different viruses, and no authority has a day-by-day contagious curve for all of them. So each falls back on what it can observe, symptoms, and on what it wants to achieve: in Germany, fewer infections at work; in Spain, fewer children needlessly kept at home.

If you are in the UK the NHS rule stands: contagious until the symptoms have gone, home only while feverish or too unwell, and the extra care reserved for newborns, the over-75s and anyone with weakened immunity.

What the guidance says in six countries

The same illness, six official positions. Where a country publishes nothing, the table says so rather than borrowing a neighbour's number.

How to stop a cold spreading at home

• Wash your hands often with warm water and soap; the NHS puts this first.
• Use tissues to trap germs when you cough or sneeze, and bin them straight away, the NHS says.
• Do not share towels or household items such as cups or children's toys with someone who has a cold, the NHS says.
• Wipe surfaces, and do not touch your eyes, nose or mouth with unclean hands, as the NHS RSV page puts it: cold germs can live on hands and surfaces for 24 hours.
• Air the room: the UKHSA's respiratory-infection guidance says to ventilate rooms you have been in by opening windows and leaving them open for at least 10 minutes after you leave.
• Keep your distance from anyone at higher risk while you have symptoms, and use a well-fitting mask near them; both are among the CDC's precautions after a respiratory illness.

Questions people ask

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Other illnesses

Contagious periods for the other illnesses covered by this tool.

This tool gives general information based on published guidance. It does not diagnose you and does not replace advice from a doctor who knows your situation. You choose the illness; we do not work out what you have.