Natural Remedies for Cold and Flu - Do They Work?

By Dr Megan Yap - PaediatricianGeneral20 Jan 2019

Hey guys!!

Here is a quick article as a follow up to the last article on probiotics.

Today I am about to knock up a quick read on various products that are marketed to “boost the immune system” or “fight off bugs” or “help ease cold and flu symptoms.” I know you guys have seen them in the shops, and I’m sure a large proportion of you may have even tried them.

Having worked as a pharmacist in a previous life, I have worked for many years in stores that sell “natural” products (that I must say – people seem to LOVE spending money on) to supposedly help immune function – BUT DO THEY REALLY WORK?  Or are you just wasting your hard earned money?

In Australia products are approved for sale by the Therapeutic Goods Administration (TGA), but it is important to note that there are 2 categories of “evidence” that are used to validate the use of complementary medicines: scientific or traditional.  The indications for most naturopathic products are based on traditional “evidence” – that is, based on theories outside modern conventional medicine (eg homeopathy, naturopathy, herbal medicine etc).  By contrast, scientific evidence is based on the clinical and scientific literature, such as trials in humans.  The LATTER is what I base my recommendations on in my day to day practise.


So what is the evidence?

Okay, off the top of my head, these are probably the most common products sold in pharmacies to “support the immune system.”

  1. Garlic
  2. Horseradish
  3. Vitamin C
  4. Echinacea
  5. Honey and lemon

Less commonly,

  1. Ginger
  2. Elderberry
  3. Eucalyptus oil

I am going to target the top 5 today – any more than that then I will be here all night looking up the evidence.  Alrighty then, here goes,


I did a quick search of the medical journal database PubMed and didn’t find any clinical trials on the combination of horseradish (Armoracia rusticana) and garlic (Allium sativum), with or without vitamin C. There were no clinical trials found on horseradish alone either.

I found a Cochrane review [i] done in 2014 that concluded there was not enough evidence from clinical trials to say that garlic prevents or treats the common cold. A trial[ii] done in 2001 suggested garlic may prevent the common cold, but the sample sizes were tiny – the treatment group only had 24 people in it, and the placebo group 65. So any suggestion of effect was based on poor-quality evidence.

A 2013 Cochrane systematic review[iii] explored whether taking vitamin C could reduce the incidence, duration or severity of the common cold. The review looked at 29 trial comparisons involving 11,306 participants and in the end, found taking vitamin C regularly failed to reduce the incidence of colds in the general population and no consistent effect was found on duration or severity of common cold symptoms.  Only a few therapeutic trials have been carried out and none have examined children.

Another 2014 Cochrane review[iv] looked at Echinacea for preventing and treating the common cold.  24 controlled clinical trials with 4631 participants were looked at that investigated several different Echinacea preparations for preventing and treating common colds or rhinovirus infections. In general, almost all trials looking at Echinacea to prevent colds showed a small preventative effect that was not statistically significant (so in the real world, this means the effect is questionable).  The evidence for treatment of colds with echinacea is weak but showed that some Echinacea products are more effective than placebo.

I couldn’t find any evidence at all for the combination of honey and lemon, but presumably the lemon is added for its vitamin C content and the evidence for that is listed above. As for honey, I found a Cochrane systematic review[v] on this published in 2018, that included 6 small trials involving 899 children.  This review found that overall, honey probably is better at relieving cough symptoms and duration compared to placebo.

Phew, and it is now 10:53pm and I have a full day of clinic to do tomorrow!  I think that’ll do for now.

I hope you found this article useful… I am really glad I wrote it actually, so now I can actually cite the references for when I tell people that they “…can try various natural remedies if they want, but they are probably wasting their money.”

In summary:

  1.  Horseradish – no evidence for effectiveness in treating or preventing common colds.
  2.  Garlic – no real evidence (ie very poor-quality evidence in tiny sample sizes) for the treatment or prevention of common colds
  3.  Vitamin C – no evidence for effect in reducing incidence of colds, no consistent effect on the duration or severity of common cold symptoms.  No studies in children.
  4. Echinacea – a small non-statistically significant preventative effect against colds, and weak evidence for some Echinacea products as better than placebo for treating colds
  5. Honey – better than placebo at relieving cough symptoms in kids


I’ll let you decide based on this evidence, whether you want to spend your money on these remedies the next time you’re at the shops!!

Catch you all soon (hopefully unlike the flu – ha ha)

xxDr Megs



[i] Lissiman E, Bhasale AL, Cohen M.  Garlic for the common cold.  Cochrane Database of Systematic Reviews. Published November 2014.  URL: . Accessed 7/1/2019.

[ii] Josling P. Preventing the common cold with a garlic supplement: a double-blind, placebo-controlled survey. Adv Ther. 2001;18(4):189-93.

[iii] Hemila H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews. Published January 2013. URL: . Accessed 7/1/2019.

[iv] Karsch-Völk M, Barrett B, Kiefer D, et al. Echinacea for preventing and treating the common cold. Cochrane Database of Systematic Reviews. Published February 2014. URL: . Accessed 7/1/2019.

[v] Oduwole O, Udoh EE, Oyo-Ita A, Meremikwu MM. Honey for acute cough in children. Cochrane Database of Systematic Reviews. Published April 2018.  URL: . Accessed 7/1/2019.


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