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• Re:No evidence for kanuka honey being an effective treatment of rosacea
  Irene E Braithwaite
  Published on: 15 April 2016
• No evidence for kanuka honey being an effective treatment of rosacea
  Harald H.H.W. Schmidt
  Published on: 24 March 2016

• Published on: 15 April 2016

  Re:No evidence for kanuka honey being an effective treatment of rosacea

  • Irene E Braithwaite, Deputy Director
  • Other Contributors:
    • Professor R Beasley, Professor Mark Weatherall

  Messrs Schmidt and Schmidt, in their letter published in BMJ Open on 24 March 2016, assert that the study we reported about the effects of Kanuka honey in rosacea has a number of important flaws including problems with the experimental treatments, study design, and statistical analysis.

  With respect to the study medications the aim of the study was not to estimate the effect of a preparation of Kanuka honey with...

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  Messrs Schmidt and Schmidt, in their letter published in BMJ Open on 24 March 2016, assert that the study we reported about the effects of Kanuka honey in rosacea has a number of important flaws including problems with the experimental treatments, study design, and statistical analysis.

  With respect to the study medications the aim of the study was not to estimate the effect of a preparation of Kanuka honey with another honey but to compare the properties of a honey treatment for rosacea against a control skin treatment. In this respect, the choice of treatment arms is clearly appropriate. Glycerine as an excipient, a pharmacologically inactive component, in the Kanuka honey preparation allows both ease of administration to the skin and also prolonged contact of the Kanuka honey with the skin. The use of excipients for this purpose in dermatological products is common. The control arm was Cetomacrogol cream. As outlined in the paper this is a non-ionic compound which itself comprises a number of excipients and which is also often used as a delivery agent for other dermatological agents. The study therefore compares, as much as possible, the potential active properties of Kanuka honey with a dermatologically neutral agent.

  We agree that it is not possible to mask participants as to the active or control therapies in a study of this nature, due to the characteristic smell and taste of honey, and that this could potentially lead to bias in the estimates of treatment effects. We have not only highlighted this potential bias in the study report but have also been scrupulous in other aspects of the study design such as masked randomisation and masked assessment of the primary outcome variable of rosacea severity. This was achieved through the same masked investigator making the visual assessments of rosacea severity without any communication with the study participants.

  With regard to the comment about statistical power, the paper presents a point estimate and confidence interval for the difference between the active and comparator arms of the trial and because the lower limit of the confidence interval is above the null, the issue of Type II error does not arise. Readers can judge for themselves the relevance of the lower or upper confidence limits of the difference. We did not specify or set out to carry out a Bayesian analysis of the experimental result in light of the anticipated rates of response. Even if we had done so, the point estimate of the relative response achieved, a relative risk of 2, was actually identical to that anticipated in the power calculation. We further note that the point estimate and confidence interval for the response rate in the active treatment group, 24/68, is 35.5% (24.1 to 47.8); and in the comparator group 12/69, it is 17.4% (9.3 to 28.4). Both of these are concordant with the response rates anticipated in the sample size calculation of 50% and 25% respectively.

  Conflict of Interest:

  The authors of this letter undertook the kanuka honey study, which is the subject of this correspondence. The study was funded by HoneyLab, who supplied the Kanuka honey product (Honevo).

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  Conflict of Interest:
  None declared.

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• Published on: 24 March 2016

  No evidence for kanuka honey being an effective treatment of rosacea

  • Harald H.H.W. Schmidt, Chair & Head of Department
  • Other Contributors:
    • Tim M. Schmidt, U. Southampton

  Braithwaite et al. [1] claim that kanuka honey is an effective treatment of rosacea. Both their study medication as well as their study design and statistical analysis are seriously flawed and do not allow this conclusion. First, the study medication is inappropriate to show an effect of kanuka honey. The verum was not kanuka honey (as the title suggests), but a mixture of kanuka honey and 10% glycerine (Honevo). As control...

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  Braithwaite et al. [1] claim that kanuka honey is an effective treatment of rosacea. Both their study medication as well as their study design and statistical analysis are seriously flawed and do not allow this conclusion. First, the study medication is inappropriate to show an effect of kanuka honey. The verum was not kanuka honey (as the title suggests), but a mixture of kanuka honey and 10% glycerine (Honevo). As control, an entirely different preparation was chosen, i.e. Cetomacrogol a mitigating and protective cream containing macrogol cetostearyl ether 22, cetiol, sorbitol and the preservative ascorbic acid, used for dry and sensitive skin, eczema and itching. This induced an obvious risk of bias and lack of blinding. Moreover, if the specific effects of kanuka honey (versus another honey) were to be tested, a different honey should have been tested with the same amount of glycerine. Second, the study would have been powered for a 25% response in the control and a 50% response in the Honevo group. However, the observed effect sizes were much lower (17.4% and 34,3%, respectively). Even if subsequently p-values less than 0.05 were calculated, no conclusions can be drawn due to this a priori lack of statistical power. Thus, both the title and the conclusion of the publication are not justified by the study design and data.

  References

  1. Braithwaite I, Hunt A, Riley J, et al. Randomised controlled trial of topical kanuka honey for the treatment of rosacea. BMJ Open 2015;5:e007651. doi:10.1136/bmjopen-2015-007651

  Conflict of Interest:

  None declared

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  Conflict of Interest:
  None declared.

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