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I have seen lots of sources claiming that thyme has antiviral properties, kills off viruses, "should be taken at first sign of a cough or cold" etc.

How supported by evidence are these claims?

I tried to do some of my own research, but found it quite hard. All I found was a paper claiming that honey is more effective against the Rubella virus than thyme is. Not very useful for the wider scale of viruses, or understanding if it has any efficacy at all.

I have been asked for references, so here are some I just found from a google search:

https://www.medicalmedium.com/blog/thyme

Thyme has a powerful ability to kill off bacteria and viruses and should be taken at first signs of a cold or illness. ... Thyme contains antiseptic, antiviral, antibacterial, carminative, diaphoretic, and expectorant properties which supports healing throughout the entire body

https://plantmedicines.org/thyme-provides-antiviral-protection-against-herpes-and-other-viruses/

Research continues to prove that Thyme (Thymus vulgaris) and its constituents can inhibit viruses such as herpes and other potent viruses

https://www.sciencedirect.com/science/article/abs/pii/S2210803318300113

Thyme extract KMTv24497 containing authorised medicinal product (Aspecton® Oral Drops) showed antiviral activity

https://www.deliciousliving.com/health/top-8-antiviral-essential-oils/

Thyme essential oil, in conjunction with tea tree and eucalyptus, has been shown to reduce viral infectivity by more than 96 percent

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  • Please see the comments below my answer and update/clarify your question as to whether your aim here is 'known antiviral activity' (or strength of effect for this) or really more like 'is this a good antiviral medication in practice'? – LаngLаngС Mar 28 at 16:44
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Yes. With ample caveats.

It shows antiviral activity in the lab, it is often used traditionally in virus-induced diseases. But as an actual prime frontline medicine against viral infection clinical evidence for its use it lacking.


Its antiviral activity is well established in vitro. But apart from laboratory settings its efficacy as an actually therapeutic agent was classified by Kommission E as an established traditional medication, but only for catarrhs of the upper respiratory tract, bronchitis and pertussis (whooping cough)'. All other, including viral infection targets, were summarily dismissed as "not enough evidence", despite ample evidence for its traditional use in a far wider applications. (Monograph 00325, BAnz. No.228/05.12.1984, BAnz. No.226/02.12.1992, BAnz. No. 50/13.03.1990. Transferred to: 12 November 2013, EMA/HMPC/342332/2013, Committee on Herbal Medicinal Products (HMPC): "Community herbal monograph on Thymus vulgaris L. and Thymus zygis L., herba", PDF). For common cold, influenza etc it is still useful as an expectorant and adjuvant. Not in the least as its anitbacterial activity is far better documented. Its aroma therapy value for similar conditions is equally well documented for use, but also lacking evidence of usefulness, simply for the lack of clinical studies.

That non-cytotoxic preparations of this herb display antiviral activities in human cell lines is evidenced in multiple studies. For example:
— Akram Astani, Jürgen Reichling & Paul Schnitzler: "Comparative Study on the Antiviral Activity of Selected Monoterpenes Derived from Essential Oils", Phytotherapy Research 24: 673–679 (2010) DOI: 10.1002/ptr.2955.
— Jürgen Reichling, Paul Schnitzler, Ulrike Suschke & Reinhard Saller: "Essential Oils of Aromatic Plants with Antibacterial, Antifungal, Antiviral, and Cytotoxic Properties – an Overview", Forschende Komplementärmedizin, 2009;16:79–90. DOI: 10.1159/000207196

An inherent problem for this essential oil product is that in the vast family of thyme species even just the one Thymus vulgaris produces a wide ranging spectrum of compounds. In its thymol fraction 1,8-cineol for example is frequent in Spanish specimen, but entirely absent in French specimen.

Another one is that frequently the volatile compounds in liquid phase inhibit or even 'kill' viruses in a petri dish but also exhibit cytotoxic activity detrimental for the host's own cells.

For systemic application this might be a problem of bioavailability and delivery. But in topical applications this is less of a problem.
— Koch C, Reichling J, Schneele J & Schnitzler P.: "Inhibitory effect of essential oils against herpes simplex virus type 2", Phytomedicine. 2008 Jan;15(1-2):71-8.

The most interesting research in that regard is that essential oil vapors were shown to be effective in such low concentrations as to be benign towards epithel cells over a short but 'long enough' timespan:

[…] Thymus vulgaris displayed 100% inhibitory activity at 3.1 μL/mL concentration. Under these conditions the vapors showed no measurable adverse effect on epithelial cell monolayers. This suggests that these oils in their vapor phases could be potentially useful in influenza therapy. The oil vapors were also evaluated for possible direct effects on the principal external proteins of the influenza virus, namely the HA (hemagglutinin) and NA (Neuraminidase). Several of the vapors inhibited the HA activity, but not the NA activity, suggesting that interaction with HA is a possible mechanism for the antiviral activity. Thus some of these oil vapors could have therapeutic benefits for people suffering from influenza, and possibly other membrane containing respiratory viruses.

— Selvarani Vimalanathan & James Hudson: "Anti-influenza virus activity of essential oils and vapors", American Journal of Essential Oils and Natural Products 2014; 2 (1): 47–53. (PDF)

Again, any conformation for efficacy in a clinical setting is lacking for this.

For more perspective on the general outlook of 'herbal essential oils againstas anti-virals', as even "peppermint is showing some antiviral activity":

— Katarzyna Wińska et al.: "Essential Oils as Antimicrobial Agents—Myth or Real Alternative?", Molecules. 2019 Jun; 24(11): 2130. doi: 10.3390/molecules24112130, PMCID: PMC6612361, PMID: 31195752

The textbook summary is thus:

Antiviral
Thyme oil demonstrates antiviral activity against HSV-1, HSV-2 and an aciclovir-resistant strain of the virus (Koch et al 2007, Nolkemper et al 2006, Schnitzler et al 2007). One study found that the oil decreased plaque formation by more than 90% when preincubated with HSV-2; however, no effect was observed when the oil was added prior to infection or after the absorption stage (Koch et al 2007). It was suggested that thyme essential oil interferes with the viral envelope.

Clinical Use Thyme has not been significantly investigated in controlled studies, therefore information is generally derived from evidence of activity and traditional use.

PATIENTS’ FAQs
What will this herb do for me?
When taken internally, thyme is used to treat bronchitis, symptoms of the common cold, diarrhoea and dyspepsia. It is also used as an antiseptic gargle for sore throats and can be diluted and applied externally to minor wounds.
Thyme has strong antibacterial activity and antifungal actions and is used as a treatment for common infections such as bronchitis and upper respiratory tract infections. It is also used as a food preservative, for relieving symptoms of dyspepsia and diarrhoea.

— Lesley Braun & Marc Cohen (eds): "Herbs & Natural Supplements. An evidence-based guide.", Churchill Livingstone Elsevier: Chatswood, 42015.

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  • 1
    I think the summary line at the top grossly overstates the rest of the evidence provided. It seems to me the answer is 'I found NO good evidence to support the claim. There were some unscientific monographs that found people use it, but that is not evidence that it works. There were some in vitro studies, but that is not evidence - see xkcd-cartoon-about-handguns.' – Oddthinking Mar 28 at 16:31
  • @Oddthinking I think the question then needs to differentiate:" is it antiviral, or is this an effective antiviral medicine?" It is clearly antiviral in vitro, used in virological conditions, but EBM is still lacking. As phrased, I think this A lists clearly enough the limitations. – LаngLаngС Mar 28 at 16:35
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    The notability references describe uses it topically, as a mouthwash, drinking it as a tea, taking it as oral drops. The question has to be about whether these treatments are effective, not whether it works as an antiseptic in a Petri dish (or we would be arguing chlorine bleach is a good antiviral agent, and suggesting people drink it is tea.) In fairness, a Cochrane paper found Thyme+Ivy is a cough-suppressant - a result that surprises me so much I am tempted to ask a question about it. – Oddthinking Mar 28 at 16:47
  • @Oddthinking XKCD is a b&w (comic). While RCT & SR of these may be 'better' evidence, traditional use and matching lab results, both compatible with host/pathogen biology are far bigger than "no evidence". For mouthwash from Q: that's about bacteria, & thyme, which works very much fine—as per RCT— as good as clorhexidin, with better taste & compliance. Anecdotal evidence also confirms thyme AV effective against labial herpes. Do you suggest I take every ref from Q to crit-praise it and/or comment on its limitations? – LаngLаngС Mar 29 at 11:14
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    XKCD provides a simple, easy-to-understand understand explanation of why in vitro results, by themselves, are not taken seriously. Anecdotal evidence of a treatment of a minor, self-remedying ailment is also not taken seriously - it accounts for a large number of health myths. – Oddthinking Mar 29 at 11:40

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