Pelargonium sidoides extract (Kaloba (R)) for the common cold

MO_10 JULY_p27This article was published in Medical Observer.

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Clinical scenario

Alan, a 30-year-old office worker looked miserable in my rooms with a runny nose, cough, and sore throat.  He had a run-of-the-mill viral upper respiratory tract infection.  He mentioned that his partner had suggested that he try “Kaloba” to help him recover.  Does it work for the common cold?

Clinical question

Is Pelargonium sidoides extract (Kaloba®) an effective treatment (symptom severity, or length of illness) for the common cold in well adults?

What does the research evidence say?

Step 1: The Cochrane Library

The Cochrane Library contains a 2013 systematic review and meta-analysis that examines the use of P. sidoides extract for acute respiratory tract infections.  Bulls-eye! [1]

Step 2: TripDatabase

Are there any newer systematic reviews or new large clinical trials since 2013?  I conducted a search using the TripDatabase PICO search tool (P: “common cold”, I: “pelargonium sidoides”, C: “placebo”, O: blank) and the Cochrane review appeared to be the best available published evidence.  So, let’s look at Timmer et al. (2013) in detail.

Critical appraisal

I will use the systematic reviews critical appraisal sheet from the Centre for Evidence Based Medicine. [2]

What PICO question does the systematic review ask?

In people with acute respiratory infections not requiring antibiotic therapy (Participants); what is the effect of P. sidoides extract (Intervention); compared to placebo or any active comparator (Comparator); on the improvement or resolution of symptoms (Outcome).

Is it clearly stated?


Is it unlikely that important studies were missed?

Yes.  The authors searched multiple electronic databases, searched clinical study registries, and contacted the manufacturer and drug approval authorities for unpublished material (p. 6). [1]

Were the criteria used to select articles for inclusion appropriate?

Yes.  The authors only included studies that were double-blind trials that compared P. sidoides extract with a placebo, or an active comparator.

Were the included studies sufficiently valid for the question asked?

Unclear, possibly not.  The authors assessed the risk of bias of the included studies, and many were at risk (Figures 2 & 3, p. 11-12). [1] The one study, Lizogub et al. (2007), that provided data for specifically for the common cold in adults was rated to be at risk of bias from inadequate blinding and outcome assessment, and at high risk of bias from selective reporting.

Were the results similar between studies?

N/A.  There was only one trial that provided data in adult participants with the common cold.

What were the results?

One study provided data on the resolution of symptoms of the common cold in adults.  Compared to placebo, P. sidoides extract did not have an effect on recovery at day 5.  However, fewer people “failed to recover” (complete resolution of all symptoms) at day 10:

  • Relative risk (RR) = 0.41 (95% confidence interval [CI], 0.29 to 0.60)


This paper appears to provide some evidence that P. sidoides extract may assist with the recovery of the common cold in adults.  If the results are to be believed from the one study, [3] the number needed to treat for complete resolution of all symptoms by day 10 is only 2!

However, we need to be quite cautious with the conclusions that we draw.  There are serious questions of bias.  The Cochrane authors considered the quality of evidence to be “very low” for the common cold, and low generally.  The studies were all by the manufacturer, and performed in the same region (Ukraine and Russia).

The funnel plot (Figure 10, p. 17) [1] of the studies is strongly suggestive of publication bias.  The larger trials found results that were close to no difference, while small trials were highly positive.  P. sidoides extract might be effective but there is substantial doubt to the effect sizes seen in the results of the existing evidence.

A pragmatic approach is that patients who want to try P. sidoides extract for respiratory tract infections to consider it from a symptomatic perspective – if they don’t think that they are finding benefit, they should stop.  It is probable that like most other herbal treatments for the common cold, P. sidoides extract is ineffective but safe.  The quality of evidence should preclude it from being recommended routinely in general practice settings.

Stat Facts

Funnel plots

A funnel plot is a diagram that typically plots the effect estimates of individual studies on the horizon axis, and a measure of the study size on the vertical axis.  Larger studies, at the top of the diagram, are more precise so the plots cluster together.  Smaller studies which are plotted lower down on the diagram, scatter more widely.  In the absence of bias, the plot should resemble an inverted funnel.


  1. Timmer A, Günther J, E Motschall, Rücker G, Antes G, Kern WV. Pelargonium sidoides extract for acute respiratory tract infections Treating. Cochrane Database of Systematic Reviews 2013, Issue 10. Art. No .: CD006323. DOI: 10.1002/14651858.CD006323.pub3.
  2. Systematic Review: Are the results of the review valid [MS Word document]? Centre for Evidence Based Medicine, University of Oxford. Last updated: 2008 Oct 1 (Retrieved: 2015 Jun 26)
  3. Lizogub VG, Riley DS, Heger M. Efficacy of a Pelargonium sidoides preparation in patients with the common cold: a randomized, double blind, placebo-controlled clinical trial. Explore 2007;3(6): 573-84. DOI: 10.1016/j.explore.2007.09.004

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