AT A GLANCE: Here are key things you will learn about the common cold from Elizabeth Hudson, DO, MPH, national physician lead and regional chief of Infectious Diseases at Southern California Permanente Medical Group, in this article:
- More than 200 viruses can cause the common cold. Rhinovirus is the most common, but adenoviruses, RSV and non-COVID coronaviruses can produce similar head cold symptoms.
- Rhinovirus signs and symptoms typically last about seven to 10 days.
- While common colds share symptoms with the flu, influenza arrives more abruptly, causes more severe body aches and fever, and can seriously sicken even young, healthy adults.
- Most people are contagious before cold symptoms begin. But you are most contagious during the first two to three days.
- Antibiotics do not work against viral infections, and supplements such as vitamin C and echinacea have little consistent evidence behind them.
- Call your doctor if cold symptoms last more than 10 days, worsen after you had started feeling better, or include a high fever, shortness of breath, wheezing or chest pain.
The common cold is an infectious disease most people will experience in their lives. Caused by more than 200 different viruses, it primarily targets the upper respiratory tract, producing the familiar cluster of head cold symptoms that most people recognize immediately, such as runny nose, sore throat, coughing, sneezing and fatigue.
Rhinovirus is the most common cause of the common cold. However, adenoviruses, respiratory syncytial virus (RSV) and other coronaviruses separate from COVID-19 can produce similar signs and symptoms.
The AMA’s What Doctors Want Patients to Know™ series gives physicians a platform to share what they want patients to understand about today’s healthcare headlines.
In this installment, Elizabeth Hudson, DO, MPH, national physician lead of infectious diseases for Kaiser Permanente and regional chief of infectious diseases for Southern California Permanente Medical Group, shares what she wants patients to know about the common cold—from understanding how rhinovirus symptoms differ from the flu, which treatments actually work, and signs that it’s time to call your doctor.
Southern California Permanente Medical Group is part of the AMA Health System Member Program, which provides enterprise solutions to equip leadership, physicians and care teams with resources to help drive the future of medicine.
Rhinoviruses are the main cause of a cold
"When I think of the common cold, it’s what we call a self-limited infection, meaning it's something that someone will get better from. It will resolve on its own,” Dr. Hudson said. “And it's a viral infection. It tends to impact our upper respiratory tract.”
“There are over 200 viruses that could potentially cause the common cold. But most commonly, the ones we see are called rhinoviruses,” she explained. “There are other types of viruses that can certainly do this—anything from adenoviruses to other kinds of coronaviruses, not COVID, but other types of coronaviruses. Even RSV is something that can give you cold symptoms.”
“Colds certainly happen year-round, but we tend to see them starting more around fall through early spring,” Dr. Hudson said. “In the winter, the air is a lot drier, and our nose has really wonderful immunological aspects to it that basically acts as a local antiviral defense. When it is very, very dry out, like in the winter, that doesn’t work as well.
“And of course, when it is cold out, people are going to be indoors more, and when you're indoors more, you just have more opportunities to get in contact with people who might potentially have a cold,” Dr. Hudson added. “The cold weather is not causing your cold. Just because you went outside, the cold weather in and of itself did not make you ill. But it's the other aspects associated with it, like a dry nose or being inside more."
Cold symptoms follow a relatively predictable timeline
"Most colds, start to finish, last about seven to 10 days,” noted Dr. Hudson. “The first couple of days—that's when you wake up in the morning, you swallow, and you notice your throat feels a little bit sore and scratchy—you might notice yourself sneezing, maybe you're just a little more tired, but it tends to come on gradually.”
“Then usually days two to four are when you feel the worst. That's when your nose really starts to get more congested, you may sneeze more, and it's very common to get a headache with it and maybe a little bit of body aches,” she explained. But usually, adults “don't get fevers when they get just a regular cold. If you do get a fever, it's likely going to be a very low-grade fever.”
The middle and later days of a cold often bring a particular misconception with them.
“Days four to seven, that's usually when you start to feel better. But it is important to know that's when you may start having more nasal discharge. And it might be thicker or a yellow color or a green color,” she said. “Those colors and that consistency in and of itself doesn't necessarily mean that you now have a bacterial infection that requires an antibiotic. It's just the” progression of a viral illness.
“Around days seven to 10, you're in the recovery phase, but you may notice a persistent cough. Sometimes it's a little worse at nighttime because of post-nasal drip,” Dr. Hudson said. “It's not uncommon for a cough to last two to three weeks after the virus, even if you're otherwise feeling OK.”
One pattern of worsening, however, should prompt a call to a physician.
“If you're getting better and then, around day six or seven, you take a turn for the worse—maybe suddenly you develop a really high fever, or you are short of breath—that would be the time to reach out to your doctor,” she said. “Maybe this has changed from a typical run-of-the-mill cold to something that might require more medical intervention. You could potentially develop a bacterial pneumonia or sinus infection.”
Colds in children and babies present differently
"For babies and kids, they get a lot more of a runny nose. They get the sneezing and the cough, and a lot of times they become very, very fussy, especially if they're very little,” Dr. Hudson said. “Babies and kids can have a little bit more of a mild fever with a cold compared to an adult.
“But the hardest thing, especially for infants, is that nasal congestion can make it very hard for them to feed,” she added.
For infants under three months, a specific threshold is non-negotiable.
"If you have a very small baby, under three months, and they have a temperature over 100.4°F, that's something that always requires going to see the doctor immediately,” Dr. Hudson said.
Over-the-counter cold medicines should never be given to young children without first consulting a pediatrician, she noted. For relief, "you can use saline nose drops or sprays and gentle nasal suction. Those are all things that are going to be safe and really the most useful for young children.”
"Children and babies get colds more often because their immune systems are still developing. They haven't had the chance to encounter all the viruses that we may have as we get older,” Dr. Hudson explained. “As we get older, we're still exposed to those same viruses, but we've already had them, and our wonderful immune system has antibodies against them.”
“Also, younger kids tend to touch their faces a lot more, share toys, and they're much less likely to wash their hands on a consistent basis,” she said. “And we know that good hand hygiene is a big part of helping stop the spread of colds. Young kids can get up to six to 10 colds a year."
There are differences between common cold vs. flu vs. COVID-19
“Definitely with the flu, the onset tends to be a little bit more abrupt, whereas a cold will kind of come on over a day or two,” Dr. Hudson explained. “Flu can sometimes come on over a couple of hours and when I have a patient who comes to me and says, 'I have the flu,' I ask them the simple question: 'Do you feel like you got hit by a truck?'
“If the answer is no, then they likely don't have the flu because the flu is something that will completely knock you back, literally, into your bed,” she added. “It's much more common to have a fever with flu.”
Additionally, “flu is more likely to potentially turn into a bacterial infection compared to just a regular rhinovirus,” Dr. Hudson said. “The flu does not discriminate, and it can make even otherwise young, healthy people very ill very quickly."
In the common cold vs. COVID-19 comparison, symptom overlap complicates matters, but a few distinguishing features stand out.
“You can get a runny nose with COVID, you can get a sore throat with COVID. You're a little more likely to get a fever with COVID versus a regular cold for adults,” she said. “But two of the biggest issues are going to be the level of fatigue and body aches and headaches, which are going to be much more severe with COVID, particularly the fatigue.”
“Then of course, COVID sometimes can make differences in your ability to smell and taste,” Dr. Hudson noted. “If you're getting cold symptoms and suddenly you notice that you can't smell the flowers or your coffee, that might indicate this is not just a regular cold—maybe you have COVID."
Colds are more contagious early on
“For most people, the first day before their symptoms start is when they can begin to spread the virus to others,” Dr. Hudson said. “People are really the most contagious within the first two to three days of symptoms.
“When you first feel that scratchy throat or your nose is starting to get a little bit stuffy, that's when you're most likely to be contagious," she added. "Usually, once you get to around day five or so, you really shouldn't be able to spread your cold germs to anyone else.”
“If you hear someone with a dry cough and you know they've been sick for a couple of weeks, they're no longer infectious,” Dr. Hudson said. “They don't sound great, but they are no longer infectious."
There is no lab test to diagnose a cold
"Usually, the common cold is something that we would diagnose clinically,” Dr. Hudson said. “We don't necessarily do a specific lab test for colds.
“However, if you go to a physician and you are presenting in respiratory virus season, you could have a cold, you could have COVID, you could have RSV,” she added. “Sometimes even some of the early symptoms of strep throat kind of overlap with this. It may be something that your clinician might want to test you for.”
Treating a cold means focusing on symptom relief
For treatment of a common cold, the honest answer is patience because “nothing can cure the infection,” Dr. Hudson said. “We call this a tincture of time—with time, it will get better. That's why we call these infections self-limited.”
“What we can do is take medication that might help us feel a little less miserable,” she noted. For example, “if you're having a fever or body aches, you can take acetaminophen or ibuprofen.
“If you're having a lot of congestion and you are an adult, you can take over-the-counter medications to help relieve nasal stuffiness,” Dr. Hudson added. “If you have a cough, you can try over-the-counter cough medicines. And if you're having a sore throat, warm fluids and lozenges can help.”
“Most of the time, the best treatments for your cold are really just going to be things that are the mildest that you can possibly take—acetaminophen, ibuprofen, and just really giving yourself a chance to rest," she said.
Antibiotics are not part of the answer.
"The reason antibiotics don't work is because they don't work against viruses,” she said.
"When you are pregnant, the only real pain reliever that you're able to take would be acetaminophen,” Dr. Hudson said. “Any other kind of over-the-counter cold medicine, if you are pregnant, you should really be talking to your clinician before starting anything like that.”
“It's important to know that for pregnant people, it's possible they could have COVID or flu, and they're a little more likely to not do as well because they are pregnant,” she cautioned.
Patients who are pregnant and have cold symptoms should be in touch with their physician to see if testing and treatment is indicated.
Frequent hand washing is key to preventing a cold
"The biggest thing is making sure that you're washing your hands frequently,” Dr. Hudson said. “You can use soap and water or an alcohol-based hand sanitizer, but that's key.”
“You really want to try not to touch your eyes, your nose, or your mouth, because those are the ways that the viruses are able to get in,” she emphasized. “When you're going to be in a crowded indoor space in the middle of peak cold and flu season, it's a good idea to consider masking up.
“And then making sure you're getting enough sleep, making sure you're eating healthy, really doing whatever you can to manage your own stress so that your immune system can function as well as possible,” Dr. Hudson added.
Be wary about vitamins and supplements to treat colds
Zinc, vitamin C, echinacea and other popular vitamins and supplements are frequently marketed as cold remedies. The evidence behind them is thin.
“There is maybe a very small amount of evidence that shows that if you take an oral zinc lozenge within 24 hours of your cold symptoms starting, it might decrease the length of your cold by one to two days,” Dr. Hudson said. “But it doesn't always necessarily prevent colds.”
Additionally, “people ask about vitamin C and echinacea, other things like elderberry and garlic,” she said. However, “there's no consistent data that shows that any of those things help to either decrease the length of your cold or help to prevent you from getting it. Bottom line, nothing is really super helpful, unfortunately.”
Call your doctor if you have worsening symptoms
“If you're getting better and then suddenly you are not, or if your symptoms are really lasting more than 10 days, that's the time to reach out to your doctor,” said Dr. Hudson. “If you suddenly have a very persistent and high fever, if you suddenly develop shortness of breath or wheezing or chest pain, those are all definitely reasons to reach out to your doctor.”
“And if you're immunocompromised, or if you're pregnant and have concerns, it's better to reach out sooner rather than later,” she emphasized. “For babies under 3 months especially, if that temperature goes over 100.4°F, the first call should be to their pediatrician."
One final point: vaccines protect against illnesses most likely to be confused with a cold—and that distinction matters.
"COVID and flu vaccines are available, and they are effective,” Dr. Hudson said. “They're not going to get rid of your cold, but they will help those other two respiratory illnesses be less severe this coming respiratory season."
