Common Cold

    Researchedby:
    Nick Milazzo

    Fact-checked

    by:

    Mike Murray, James Gaylor
    Last Updated: October 13, 2024

    “The common cold” is a catch-all term for certain mild viral upper respiratory tract infections. There are no cures for the common cold; treatments are focused primarily on improving symptoms. Fortunately, colds typically resolve on their own in 2–14 days.

    Common Cold falls under the Immunity & Infectious Disease category.

    44 references on this page
    28,554 participants in 75 trials and 5 meta-analyses

    What is the common cold?

    Although “the common cold” is typically treated like a single condition, it’s actually a generic term for mild upper respiratory tract infections caused by viruses (such as rhinovirus, respiratory syncytial virus, human metapneumovirus, and non-COVID coronavirus, to name a few). It’s one of the most common illnesses in the world — adults will get 2–3 colds each year, on average, and children can get many more.[1] [2]

    What are the main signs and symptoms of the common cold?

    One of the key differences between colds and the flu is symptom severity. Colds tend to be mild; the flu is often more severe, and the latter may not involve upper respiratory symptoms at all.[3]

    • Fever (common in children; less common in adults)
    • Runny or stuffy nose
    • Green or yellow nasal discharge
    • Sore throat
    • Coughing/sneezing
    • Fatigue
    • Muscle aches
    • Headache

    How is the common cold diagnosed?

    Colds are frequently self-diagnosed. In a clinical setting, they are primarily diagnosed based on a clinician’s impression of their patient’s symptoms. Typically, a “cold” is distinguished from the flu based on how quickly the symptoms come on and how severe they are. Historically, it’s been rare for clinicians to perform diagnostic tests, but post-COVID-19, it’s becoming more common.

    What are some of the main medical treatments for the common cold?

    There are no cures for the common cold; treatments are focused on managing symptoms until the cold ultimately resolves on its own. For this purpose, people may use:

    • Anti-inflammatory medications such as non-steroidal anti-inflammatory medications (NSAIDs) or acetaminophen.[4][5]
    • Decongestants such as ephedrine and pseudoephedrine.[6]

    Have any supplements been studied for the common cold?

    Again, no supplements can cure the common cold. However, zinc seems to quite reliably reduce symptom duration. Echinacea, Pelargonium sidoides, and garlic may also be helpful for reducing symptom duration, but there’s not enough research to know definitively.

    How do I know if micronutrients might be beneficial for me?

    Which supplements can help against colds and the flu?

    How could diet affect the common cold?

    Diet is mainly related to the common cold through immunity. Diets that are sufficient in energy, micronutrients, and macronutrients are important for maintaining a robust immune system, which will help reduce the risk and severity of common cold infections.[7] Flavonoids (plant compounds that have antioxidant and immunomodulatory properties; found in especially high quantities in tea, chocolate, capers, and oregano)[8] may be a noteworthy nutrient for this purpose.[9]

    Are there any other treatments for the common cold?

    Saline nasal and sinus irrigation (using devices like a neti pot or a nebulizer) may improve cold symptoms. However, it’s very important to only use water that has been filtered, sterilized, or otherwise treated for such uses — serious infections can occur otherwise.[10]

    Some trials report that meditation and exercise may reduce the risk and severity of the common cold.[11][12]

    What causes the common cold?

    The common cold is caused by a large number of viruses. Over 200 viruses have been identified as causing colds, many of which are classified as rhinoviruses. These viruses are constantly present in the environment, and infection can occur from physical contact with infected people or surfaces, breathing in small-particle aerosols containing virus in the air, or being directly hit by large-particle aerosols from a person coughing or sneezing.[13][1] Infections are most common in the winter and spring and during rainy seasons in tropical areas.[13]

    Examine Database: Common Cold

    Research FeedRead all studies

    Frequently asked questions

    What is the common cold?

    Although “the common cold” is typically treated like a single condition, it’s actually a generic term for mild upper respiratory tract infections caused by viruses (such as rhinovirus, respiratory syncytial virus, human metapneumovirus, and non-COVID coronavirus, to name a few). It’s one of the most common illnesses in the world — adults will get 2–3 colds each year, on average, and children can get many more.[1] [2]

    What are the main signs and symptoms of the common cold?

    One of the key differences between colds and the flu is symptom severity. Colds tend to be mild; the flu is often more severe, and the latter may not involve upper respiratory symptoms at all.[3]

    • Fever (common in children; less common in adults)
    • Runny or stuffy nose
    • Green or yellow nasal discharge
    • Sore throat
    • Coughing/sneezing
    • Fatigue
    • Muscle aches
    • Headache
    How is the common cold diagnosed?

    Colds are frequently self-diagnosed. In a clinical setting, they are primarily diagnosed based on a clinician’s impression of their patient’s symptoms. Typically, a “cold” is distinguished from the flu based on how quickly the symptoms come on and how severe they are. Historically, it’s been rare for clinicians to perform diagnostic tests, but post-COVID-19, it’s becoming more common.

    What are some of the main medical treatments for the common cold?

    There are no cures for the common cold; treatments are focused on managing symptoms until the cold ultimately resolves on its own. For this purpose, people may use:

    • Anti-inflammatory medications such as non-steroidal anti-inflammatory medications (NSAIDs) or acetaminophen.[4][5]
    • Decongestants such as ephedrine and pseudoephedrine.[6]
    Have any supplements been studied for the common cold?

    Again, no supplements can cure the common cold. However, zinc seems to quite reliably reduce symptom duration. Echinacea, Pelargonium sidoides, and garlic may also be helpful for reducing symptom duration, but there’s not enough research to know definitively.

    How do I know if micronutrients might be beneficial for me?

    If you are healthy and eat a well-balanced, diverse diet, chances are you don’t need a micronutrient supplement. However, in special cases, micronutrient supplementation could make sense. People with deficiencies often benefit more from micronutrient supplementation. For example, vitamin D supplementation is most beneficial for people with low baseline levels.[14] However, people with sufficient baseline levels showed only a slight risk reduction for acute respiratory infection. Another example is high-performing athletes, especially during periods of intensified training and/or competition. A Cochrane review[15] showed that marathon runners, skiers, and soldiers performing subarctic exercises showed a substantial risk reduction (RR 0.48) of getting a cold when supplementing vitamin C. If you are a high-performing athlete, this could make a practical difference to your performance.

    In general, beware of toxic overdosing and the potential side effects when supplementing minerals such as zinc[16] and water-insoluble vitamins such as vitamin D[17]. Overall, the usefulness of micronutrient supplementation most often requires individual consideration. Hence, it’s difficult to make any generalized recommendations.

    Which supplements can help against colds and the flu?
    Quick answer:

    Vitamin C, vitamin D, zinc, and other supplements may provide an edge against colds and the flu, but they should only serve to complement your main defensive arsenal: good hygiene, proper hydration, healthy diet, restful sleep, stress control, and exercise.

    Colds and the flu are caused by viruses that travel from person to person. Although you fend off infections year round, you may be more vulnerable during the colder months: the ambient cold may weaken your immune system, according to preliminary human[18] and animal[19] evidence, and if it makes you spend more time inside with other people, it also gives you more opportunities to trade viruses and microbes. image

    Unfortunately, even if you follow these best practices, you can still get unlucky and catch a cold or contract the flu. This is why, once winter hits, one of the most popular questions we get is: among the many supplements used to ward off an infection or lessen its symptoms, are there any that work?

    The answer is a tentative yes. In this article, we’ll review four supplements whose benefits are backed by moderate evidence and four whose benefits are backed by only preliminary evidence.

    Supplements with moderate evidence

    The evidence regarding the benefits of vitamin C, vitamin D, and zinc is often mixed, but it suggests a positive effect.

    Vitamin C

    Vitamin C is marketed as the go-to supplement for preventing and treating colds.

    Mechanistically, it makes sense: vitamin C helps immune cells form and function, and it supports the physical barriers (such as the epithelial cells of your skin) that protect you from pathogens.[20] Moreover, at least 148 animal studies have found that vitamin C administration helps prevent infections caused by microorganisms.[21]

    Those animal studies, however, don’t answer the question that most matters to us: can vitamin C supplementation help humans ward off colds? A 2013 Cochrane meta-analysis of human studies tried to answer this question,[15] and here are the takeaways:

    • People who start taking vitamin C when they already have a cold don’t appear to see much of a benefit. Some studies suggest that very high doses (several grams) might reduce the duration of colds, but more studies are needed for confirmation.
    • People who take vitamin C regularly can expect shorter colds (by 8% in adults and 14% in children) with slightly less severe symptoms.
    • Athletes who take vitamin C regularly are half as likely to catch a cold as athletes who don’t. Only people who “perform regular or acute bouts of intense exercise” seem to enjoy this benefit.

    A 2018 meta-analysis also supports the idea that vitamin C can shorten colds and lessen symptoms.[22] It included only 9 trials, however, all of which were among the 29 trials included in the 2013 Cochrane meta-analysis.

    Vitamin C can reduce the duration of colds (and even help ward them off, if you’re an athlete), but only if you’ve been supplementing regularly. If you start when you’re sick, it’s probably too late.

    Vitamin D

    Vitamin D receptors are found throughout the body, and vitamin D is involved in many cellular processes, including the regulation of immune cells during infections,[23][24] so it should come as no surprise that a deficiency can impair immunity.

    Epidemiological studies show an association between low vitamin D levels and a higher risk of viral infections of the upper respiratory tract (URT). [25][26] According to a 2017 systematic review and meta-analysis of individual participant data from randomised controlled trials, taking vitamin D could help prevent asthma symptoms as well as URT infections.[27] More may not be better, however: a randomized trial published the same year found no statistically significant difference in incidence and duration of URT viral infections between children taking 400 IU/day and children taking 2,000 IU/day.[28]

    Vitamin D serves many functions in the body, and a deficiency may impair immunity. A large systematic review suggests that supplementation may help prevent upper respiratory infections.

    Zinc

    Zinc plays many roles in the body — including several in the immune system alone. If you easily catch colds, make sure your diet provides you with enough zinc. Athletes and other people who sweat a lot are at greater risk of zinc insufficiency, but taking too much zinc is aso a risk, so be careful.

    Zinc lozenges can limit virus replication at the nasal epithelium and may reduce respiratory tract inflammation. Sucked throughout the day (75–95 milligrams of zinc per day, starting within 24 hours of symptom onset), they can reduce the duration of a cold by 2–4 days, though symptoms may persist for a few days thereafter.[29][30] Lozenges with zinc acetate may be more effective than lozenges with zinc gluconate (a more common form), but the trials are few, and a recent meta-analysis failed to find a significant difference.[31]

    Zinc lozenges can cause nausea and dysgeusia (a change in taste perception), but those symptoms stop when supplementation stops.[29][30] In addition to nausea and dysgeusia, zinc nasal sprays can cause anosmia,[32] and this loss of smell perception may persist after supplementation has stopped. For that reason, and because the sprays have not been shown to be more effective than the lozenges, the sprays are not recommended.

    The zinc dose shown to reduce the duration of colds (75–95 mg/day[29][30]) is above the safe upper limit (40 mg/day). You should suffer no harm if you take up to 100 mg/day for up to two weeks, but if you start suffering from nausea, vomiting, loss of appetite, stomach cramps, diarrhea, or headaches, all signs that you may be taking more zinc than your body can stand, just stop supplementing with zinc. Also, remember that zinc is present in foods and in many supplements, notably multivitamins: make sure that you don’t end up taking more zinc than you planned to.

    Taking zinc lozenges throughout the day, starting from the very first symptoms of a cold, may reduce the duration of the illness, but supplementation should not exceed 100 mg of zinc per day for up to two weeks. Since zinc nasal sprays might cause a lingering loss of smell perception, they’re better avoided.

    Supplements with preliminary evidence

    Many other supplements might help reduce the duration and severity of colds and the flu, but the evidence tends to be mixed, scarce, or low in quality. Among the most promising supplements are echinacea, elderberries, Pelargonium sidoides, and probiotics.

    Echinacea

    Taken daily, echinacea might reduce the risk and duration of upper respiratory infections,[33] yet trial effects are so small as to lack statistical or clinical significance.[34] Moreover, many of the trials were low in quality, or their quality was difficult to determine.

    Echinacea can interact with medications, particularly immunosuppressive drugs. If you take any medication, you may want to consult a physician before trying this supplement.

    Echinacea might reduce the risk and duration of upper respiratory infections, but many of the studies are of low quality and the effects are very small at best.

    Elderberries

    Elderberries (the fruits of the elderberry shrub) are known for their antioxidant properties, and in one randomized controlled trial, an elderberry extract reduced the duration and severity of colds more than placebo.[35] Also, a few human trials have shown elderberries to reduce symptoms of the flu,[36] but here the evidence is weakened by small sample sizes and, in some cases, low methodological quality.

    Due to the small number of studies, both the efficacy and safety of elderberries are still in doubt.[37] Should you choose to prepare elderberry juice yourself, rather than to purchase a supplement, remember that the berries must be properly cooked, since they can otherwise cause nausea or, worse, cyanide toxicity. Only ever use the berries — the rest of the plant is poisonous and should not be consumed in any form.

    Elderberries are a promising but understudied supplement: they may reduce the symptoms of colds and the flu, but the evidence is still preliminary. Beware: the plant is poisonous, and even the berries can be dangerous if not prepared properly.

    Pelargonium sidoides

    Pelargonium sidoides contains prodelphinidins — tannins that can help prevent bacteria from attaching to the lining of the throat and lungs. Pelargonium sidoides may reduce the duration and severity of colds,[38][39] but the studies are few and haven’t been critically appraised in systematic reviews. In addition, none of the studies were designed to see if Pelargonium sidoides could ward off colds.

    Pelargonium sidoides seems to reduce the duration and severity of colds, but the evidence is still preliminary.

    Probiotics

    Various probiotics have been shown to interact with immune system cells,[40] but a 2015 report summarizing 17 Cochrane systematic reviews found no high-quality evidence that probiotics could prevent illnesses.[41]

    Since then, a different systematic review and meta-analysis of 23 randomized controlled trials (RCTs) has found that probiotics appear to decrease the incidence of respiratory tract infections (RTIs) in children,[42] and two RCTs reported that specific probiotics might help prevent upper RTIs in athletes[43] and the elderly,[44] but the Cochrane reviews are still the most reliable evidence we have.

    Truth is, systematic reviews of probiotics studies are difficult to perform, for two reasons:

    • Different studies used different bacterial strains, so their comparability is low.
    • Some studies combined strains, making it impossible to determine which strain or strains caused the effects noted.

    With regards to the flu, a 2017 meta-analysis of 9 RCTs found that taking probiotics and/or prebiotics helped improve the efficacy of the flu vaccine in healthy adults when supplemented around the time of vaccination. However, many of the trial participants were healthy older adults, often above the age of 70, and we can’t be sure the benefits extend to a younger population.

    Probiotics might help prevent respiratory tract infections, but the evidence is of low quality. Several studies suggest that probiotics may increase the efficacy of the flu vaccine in healthy, older adults.

    Recommendations

    Reaching for a supplement or two can seem like a quick, simple way to defend yourself against colds and the flu. Be it for prevention or treatment, however, even taking the best supplements won’t help as much as following these best practices: image

    So, as always, choose efficacious supplements to complement your healthy habits — not to make up for a lifestyle that predisposes you to getting sick.

    If you’re looking for information on optimal dosages and combinations, then you may be interested in our Allergies & Immunity Supplement Guide.

    How could diet affect the common cold?

    Diet is mainly related to the common cold through immunity. Diets that are sufficient in energy, micronutrients, and macronutrients are important for maintaining a robust immune system, which will help reduce the risk and severity of common cold infections.[7] Flavonoids (plant compounds that have antioxidant and immunomodulatory properties; found in especially high quantities in tea, chocolate, capers, and oregano)[8] may be a noteworthy nutrient for this purpose.[9]

    Are there any other treatments for the common cold?

    Saline nasal and sinus irrigation (using devices like a neti pot or a nebulizer) may improve cold symptoms. However, it’s very important to only use water that has been filtered, sterilized, or otherwise treated for such uses — serious infections can occur otherwise.[10]

    Some trials report that meditation and exercise may reduce the risk and severity of the common cold.[11][12]

    What causes the common cold?

    The common cold is caused by a large number of viruses. Over 200 viruses have been identified as causing colds, many of which are classified as rhinoviruses. These viruses are constantly present in the environment, and infection can occur from physical contact with infected people or surfaces, breathing in small-particle aerosols containing virus in the air, or being directly hit by large-particle aerosols from a person coughing or sneezing.[13][1] Infections are most common in the winter and spring and during rainy seasons in tropical areas.[13]

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