Colds and flu: the herbal remedies that have evidence (and the others)

Every fall, it is the same story. The kids come home from daycare with runny noses, the office starts coughing, and we look for something that might help without running to the pharmacy for every sniffle. The reflex is often to turn to "grandma's remedies" or natural products: honey, elderberry syrup, echinacea, herbal teas, vitamin C.

Some have been seriously studied. Others rest mostly on tradition. And a few can cause problems if you do not know the precautions. This guide sorts them out, based on Cochrane reviews, which gather all the quality studies on a question, on Health Canada and on the National Center for Complementary and Integrative Health (NCCIH), a U.S. public agency.

This article is for information only and does not replace the advice of a health professional.

First: colds, flu and when to see a doctor

Colds and the flu are both viral infections of the respiratory tract, but they are not quite alike. According to Québec.ca, the flu often starts with a sudden fever, a sudden cough, a sore throat and extreme fatigue. In older people, it may show up only as weakness or confusion. A cold mostly brings a runny or stuffy nose, sneezing and a sore throat, usually without a high fever.

Most healthy people recover from the flu on their own in 5 to 8 days, according to Québec.ca. Rest, plenty of fluids, and if needed acetaminophen or ibuprofen for fever and pain: that is the foundation. No natural remedy replaces it.

See a doctor if the fever persists, if breathing becomes difficult or if the skin changes colour. If in doubt, 811, option 1, puts you in touch with an Info-Santé nurse, who assesses the situation and tells you whether you need to see a doctor, and when. In an emergency, call 911.

And for the flu, Québec.ca is clear: the best way to protect yourself from complications is to get vaccinated. No plant has comparable evidence.

How to read the word "evidence"

A remedy can look proven for several reasons that have nothing to do with each other. Before getting to the plants, here are three ideas that help.

• A systematic review, like Cochrane's, gathers all the quality clinical trials on a question and draws an overall conclusion. It also gives a level of certainty: high, moderate, low or very low. Low certainty means the result could change with better studies.
• Traditional use means a plant has long been used for a given problem. That is real information, but it is not the same as a clinical trial against a placebo.
• Licensing by Health Canada is recognized by the NPN on the label. It can be based on clinical studies or on traditional use. In the latter case, the elder monograph, for example, words the claim with the term "Herbal Medicine". To understand it all, see our article on reading a natural health product label.

The table: remedy by remedy

This table sums up the state of knowledge at the time of writing. The following sections give the details.

Honey: the best supported, but not before age 1

Of all kitchen remedies, honey for cough has the most evidence. The Cochrane review by Oduwole and colleagues, updated in 2018, brings together 6 trials and 899 children aged 1 to 18 who were coughing because of a respiratory infection.

• Compared with no treatment or a placebo, honey probably relieves cough better (moderate certainty).
• Compared with dextromethorphan, a common ingredient in cough syrups, it may have a similar effect (low certainty).
• Compared with diphenhydramine, an antihistamine, it may be better (low certainty).

The authors note that most children were treated for only one night, which limits the scope of the results. In the best-known trial, Ian Paul's in 2007, children received a single dose 30 minutes before bedtime, and buckwheat honey improved the sleep of both the children and their parents.

The precaution is not up for debate: never give honey before age 1. According to Health Canada, honey can contain spores of Clostridium botulinum, the bacteria that causes infant botulism. Babies do not yet have the gut bacteria that protect them, and neither pasteurization nor cooking easily destroys these spores. Learn more in our article on honey for cough.

Elderberry: a monograph, few trials

Elderberry syrup has become a pharmacy classic. Health Canada has published an elder monograph, updated in December 2025, which covers European black elder and Canadian elder. It allows products made from dried flowers or fruit to be licensed to help relieve cold and flu symptoms, and the fever that comes with them, in Herbal Medicine. In other words, the claim is based on traditional use, not on clinical trials.

An interesting detail for foragers: Canadian elder is the shrub with large flat clusters of black berries that you see along ditches and fields in Quebec. For dried fruit, the monograph allows 1.3 to 18 g per day in adults, and it does not provide for any use before age 2.

On the research side, the systematic review by Wieland and colleagues, published in 2021, found only 5 clinical trials on viral respiratory infections. In adults who caught a cold anyway, elderberry might shorten the illness by about two days and make it less severe. For the flu, the effect on duration is very uncertain. The authors rate the certainty of evidence as moderate to very low, and call for larger studies.

Safety, for its part, requires attention. According to the NCCIH, raw or unripe elderberries, leaves and stems contain compounds that can cause nausea, vomiting and severe diarrhea; cooking destroys these compounds. Homemade syrup is therefore always made with ripe, well-cooked berries. All the details are in our article on elderberry syrup.

Echinacea: many studies, few results

Echinacea, the purple flower of garden beds, is probably the most studied plant for colds. The Cochrane review by Karsch-Völk and colleagues, published in 2014, brings together 24 double-blind trials and 4,631 participants.

Their conclusion: echinacea products have not been shown to provide benefits for treating a cold. For prevention, none of the 12 individual comparisons found a significant difference; pooling the results suggests a relative risk reduction of 10 to 20%, an effect the authors consider of questionable clinical relevance. They also point out that the products tested varied enormously: different species, different plant parts, different preparations.

On safety, dropouts and adverse effects were not significantly different between echinacea and placebo. The authors do note, in the prevention trials, a trend toward more dropouts due to adverse effects among people taking echinacea.

In practice, this means a jar of echinacea does not necessarily resemble the one tested in a study. For the details and numbers, see our article on what the Cochrane review concludes about echinacea.

Herbal teas: comfort, and sometimes a little more

A hot cup feels good when your throat hurts, and drinking often is part of the basic care recommended by Québec.ca. So an herbal tea is a good idea, whatever the plant. The question is whether the plant itself adds anything.

Balsam fir

In Quebec, balsam fir tea has a long history. Among the Cree of James Bay, the Cree Board of Health and Social Services describes a traditional preparation of boiled fir branches, drunk warm to help sleep and relieve cough, sore throat and congestion. The fact sheet recommends a maximum of 2 to 3 cups per day, and advises against this medicine, like any other traditional medicine, during pregnancy or breastfeeding, except under the direct advice of a traditional healer.

No clinical trial has evaluated this tea for colds. And there is one important precaution: identify the tree correctly so you do not confuse it with Canada yew, a shrub with flat needles that is toxic. Everything is explained in our article on balsam fir tea.

Rose hips

The fruit of the wild rose is rich in vitamin C when fresh, and makes a very pleasant tangy tea. Our rose hip tea recipe explains how to make it, and our article on rose hips and vitamin C shows how much really ends up in the cup.

The others: vitamin C, zinc, garlic

They are not plants in the strict sense, but they sit on every shelf right next to elderberry and echinacea.

Vitamin C. The Cochrane review by Harri Hemilä and Elizabeth Chalker, published in 2013, brings together 29 comparisons and 11,306 participants for prevention. The result: taken daily, vitamin C does not reduce the number of colds in the general population. The exception is people under brief, extreme physical stress, such as marathon runners, skiers or soldiers, in whom the risk was roughly halved. Taken daily, it shortens colds by 8% in adults and 14% in children. But started after the first symptoms, it has no consistent effect.

Zinc. According to the NCCIH, zinc lozenges might shorten a cold if you start taking them within 24 hours of the first symptoms. On the other hand, zinc applied in the nose has been linked to a loss of the sense of smell, and should not be used.

Garlic. A Cochrane review cited by the NCCIH did not find enough clinical trials to conclude that garlic prevents or treats colds. It is still excellent in soup, which is not so bad.

Probiotics. They show up more and more in "immunity" products. According to the NCCIH, there is not enough research to know whether they prevent colds, and their long-term safety is still poorly understood.

Saline nasal rinse: simple, but with the right water

It is not a plant, but it is one of the few home remedies with reasonable support. According to the NCCIH, rinsing the nose with salt water might relieve cold symptoms in children and adults alike. It helps clear a stuffy nose and flush out secretions.

The important precaution concerns the water. The U.S. Food and Drug Administration (FDA) points out that tap water is not adequately filtered or treated to be put in the nose: bacteria and amoebas can survive in it and cause serious, though rarely fatal, infections. Use:

• distilled or sterile water;
• or tap water boiled for 3 to 5 minutes, then cooled until lukewarm, kept in a clean closed container, and used within 24 hours.

Wash and dry the device between uses. For children, the FDA notes that some can use it from around age 2, but only if a pediatrician recommends it.

Why so many remedies seem to work

If the evidence is so thin, why do so many people swear their syrup or tea works? There are good reasons for that, and none of them is naivety.

• Colds get better on their own. We often take a remedy when symptoms are at their worst, and feel better a few days later. That would have happened anyway, but we credit the remedy.
• The placebo effect is real for symptoms like cough or sore throat. That is exactly why good studies compare a remedy with a placebo, not just with nothing.
• Warm and sweet bring relief. A hot drink soothes the throat, and honey coats it. That relief is real, even if the plant in the cup has nothing to do with it.

None of this stops you from having a tea that makes you feel better. Just avoid paying a lot for a promise, or delaying a needed consultation while waiting for the remedy to kick in.

Children: different rules

With children, you need to be even more careful, with natural products as with medications.

• No cough and cold medicines before age 6. Health Canada says these over-the-counter products are contraindicated in children under 6: there is little evidence they work in this age group, and cases of misuse, overdose and serious side effects have been reported.
• No honey before age 1, nor products that contain it.
• A natural health product is a health product. Health Canada advises consulting a health professional before giving one to a child. The elder monograph, for example, does not provide for use before age 2.
• See a doctor, according to the INSPQ, if a baby under 3 months coughs a lot, if the child coughs to the point of choking or vomiting, if the cough has lasted more than 10 days, or quickly if the child has trouble breathing.

Buying a product: good habits

If you choose to try a natural health product, a few simple habits help you avoid bad surprises.

• Look for the NPN on the label: according to Health Canada, it is an eight-digit licence number preceded by the letters NPN. It shows that the product has been assessed. For a homeopathic remedy, it is DIN-HM.
• Read the warnings: pregnancy, breastfeeding, allergies, duration of use. For elder, for example, Health Canada requires a statement to consult if symptoms persist or worsen.
• Talk to your pharmacist if you take medications: they can check for interactions.
• Be wary of promises: a product that claims to "boost immunity" or "cure the flu" goes further than the studies allow.

In short

For colds and flu, the best-supported natural remedy is also the simplest: a spoonful of honey at night for cough, from age 1. Elderberry has a Health Canada monograph and a few encouraging studies, but of low certainty. Echinacea has been studied a lot, with few results. Vitamin C does not prevent colds in most people. And herbal teas, fir or otherwise, comfort and hydrate, which is no small thing.

For the rest, the old advice still holds: rest, fluids, handwashing, and the flu shot to avoid complications. And when things are not going well, call 811.

Sources

• Honey for acute cough in children, O. Oduwole, E. E. Udoh, A. Oyo-Ita and M. M. Meremikwu, Cochrane, 2018.
• Echinacea for preventing and treating the common cold, M. Karsch-Völk et al., Cochrane, 2014.
• Vitamin C for preventing and treating the common cold, H. Hemilä and E. Chalker, Cochrane, 2013.
• Natural Health Product: Elder (Sambucus), Health Canada, 2025.
• Elderberry for prevention and treatment of viral respiratory illnesses: a systematic review, L. S. Wieland et al., BMC Complementary Medicine and Therapies, 2021.
• The Common Cold and Complementary Health Approaches, National Center for Complementary and Integrative Health, 2020.
• European Elder, National Center for Complementary and Integrative Health, 2024.
• Infant botulism, Health Canada.
• Information about the flu (influenza), Government of Quebec.
• Concerns about children's medication, Health Canada.
• Traditional Medicine: Balsam Fir, Cree Board of Health and Social Services of James Bay.
• Toux chez l'enfant (in French), Institut national de santé publique du Québec, 2026.
• Is Rinsing Your Sinuses With Neti Pots Safe?, U.S. Food and Drug Administration.