House dust mite control measures for asthma have no effect but that’s not what you hear

Three decades of nonsense and dishonesty

Some people with asthma are allergic to house dust mites, and many physical and chemical methods have been tried against mites.

Little did I know, when I decided to do a Cochrane review of the randomised trials in 1996, that this therapeutic area was dominated by dishonesty, fraud and corruption, which would continue to this day, and that we would be exposed to serious editorial misconduct in Cochrane.

The Cochrane fraud

None of the interventions have any effect,¹ but our results were not welcomed in Cochrane. The editor of the Cochrane Airways Group, Paul Jones, said he needed total certainty that our data extraction was correct, which was surprising. We were a strong team of people, including a lung specialist who had done more trials than anyone else.

Jones asked us to review all the trials again and demanded we go to the group’s office in London to work there while “consulting” the editorial staff, as he called it.

We didn’t need help from people who were less qualified than us, and the extra work was a total waste of time. It didn’t change anything, but delayed publication of our review considerably, which was intended. I learned later that, in the meantime, an application for a trial, similar to many of those we had reviewed but much larger, had been granted public funding amounting to the huge sum of £728,678. If our review had been out, the trial would likely not have been funded.

This institutional corruption² in Cochrane was just the start of our troubles. After our review had been approved for publication, Jones secretly changed our abstract. We incidentally detected this and complained about it.

Some years later, when we updated the review with new trials, Jones changed our abstract again - and again without our knowledge or permission. This was serious editorial misconduct.

We concluded that the interventions “seem to be ineffective and cannot be recommended,”³ which Jones changed to, “There is not enough evidence to show” that the interventions were effective. This was falsely called “Reviewers’ conclusions.” To say that “there is not enough evidence” suggests that if we could have included the large UK trial, we might have shown that the methods worked.

As fraud is any activity that relies on deception to achieve a gain,⁴ Jones committed fraud. We had shown, with narrow confidence intervals, that we could not have missed a worthwhile effect. In our most recent update of the review, from 2008, there is still no trace of an effect, and the large UK trial made no difference to our results whatsoever.⁵ With my statistical background, I knew that this would be the case.

Misleading guidelines

The editor of Allergy had become so tired of his colleagues who turned a blind eye to our review when recommending useless interventions against mites that he, in 2007, asked us to publish it in his journal, which we did.⁶ He was particularly concerned about new asthma guidelines published by the US National Institutes of Health.⁷ An editorial in The Lancet called them “rigorous and evidence-based,” but we explained that this was not correct for the house dust mite recommendations.⁸

The guidelines were 440 pages, the size of two books. An expert panel recommended mattress covers quoting an editorial, a non-systematic review, a before/after study with no control group, a study about rhinitis, and a study we excluded from our review because there were no data for patients who were allergic to mites. Another study was irrelevant because it involved multiple interventions and allergens. The remaining five trials didn’t show an effect of mattress covers. We had 26 trials of mattress encasings in our review and there was no effect.

It was amazing that this deception came from the NIH. The eminences said nothing about our review, which was widely known and had been published in the BMJ nine years earlier.¹

In our Allergy paper, we mentioned a 2008 consensus report written by expert teams from two European academies.¹⁰ It listed impermeable mattress, pillow and quilt covers but forgot to say that they don’t work. JAMA called the guidelines evidence-based, and one of the authors said: “We tried very hard to make these recommendations evidence-based and tried to avoid expert opinion as the basis for recommendations.”¹⁰

I noted in a letter to JAMA that the experts had not tried hard enough because the three references offered in support of their recommendations were irrelevant. I also said that we found that the average effect of the interventions on the peak expiratory flow rate - the most common outcome in asthma trials - was exactly zero, with a very narrow confidence interval.

JAMA refused to publish my letter. Institutional corruption again. My letter made it clear that JAMA had deceived its readers but if JAMA admitted this, they would lose prestige.

Of mites and men

I have experienced that for many doctors - whether they are investigators, clinicians or journal editors - it doesn’t matter that they deceive the patients.¹¹ Patients have been lured into accepting highly expensive super-vacuum cleaners, mattress covers, obsessive cleaning, air filters and throwing out carpets.

I was so appalled over all this that I decided to do a study of narrative reviews to see how deep the fraud was. Inspired by John Steinbeck’s novel, Of mice and men, we called our paper, Of mites and men.¹² We found that 90% of the 70 reviews we included recommended physical interventions, with a highly biased sample of references in support of this. The most quoted trial had only 7 patients per group; its significant result was erroneous; and it was not a clinical outcome.

The recommendations were often based on non-randomised studies, and the most quoted observational study had only 10 patients per group but claimed very positive results. We had 54 randomised trials and 3002 patients in our review.

In 2013, a survey showed that most Italian paediatricians recommend mattress covers, weekly washings at high temperatures, special vacuum cleaners and removing carpets.¹³ The authors presented unwarranted criticism of our review and concluded that the best strategy was to implement all preventive measures. They acknowledged that it is impossible to eradicate mites because they invade houses from the environment,¹⁴ but this admission had no impact on their recommendations.

It was equally bad elsewhere. The text from the famous Mayo Clinic in the US was contradicted by the science:¹⁵ “When you minimize your exposure to dust mites, you can expect fewer or less severe allergic reactions.” The authors recommended even more futile interventions than the Italian doctors, with no references, which means no accountability.

The UK charity Asthma + lung UK also failed miserably.¹⁶ It had similar recommendations as the Mayo Clinic and advised to “open your windows regularly,” which will ensure that more mites will enter the house!

The stupidity peaks in Denmark

When the Appeals Board in 2009 overturned a decision about paying for a mattress cover for one of his patients, Danish paediatrician Jesper Brandt Andersen called the decision grotesque and wrote an article about it in our medical journal.¹⁷

I replied that the Appeals Board based its decision on our Cochrane review after having obtained an opinion from the Board of Health. Strangely, however, the Board continued to recommend mattress covers and said it was in dialogue with “doctors with great expertise in this area.”¹⁸

Splendid. When the best evidence we have doesn’t please people with conflicts of interests, our authorities no longer refer to evidence but to eminence.

In the Board’s 94-page handbook on allergic disorders, there was no reference to our Cochrane review, only to a small Danish trial with 47 patients, which did not find any effect on asthma symptoms. I noted that “doctors with great expertise,” both at home and abroad, after having had 11 years to think about our review, had not changed anything in their recommendations.

My attempt at bringing a little reason into the debate angered Andersen who wrote a new article that was full of untenable arguments and misquotations. He even claimed that our Cochrane review was not evidence-based medicine!¹⁹

I got the point. If you don’t like the results of a randomised trial, just claim it was not a randomised trial.

The allergy “experts” were dishonest, as they must have known that the interventions cannot work. The reduction in allergens that can be obtained is far too small to have any effect, and there are lots of mites in the environment that continue coming into the house.

In 2010, Danish experts on mites said in an interview that encasing mattresses could not work because there are extremely few mites in the mattress compared to the rest of the house.²⁰ One of them noted that wrapping the mattress in allergen-proof mattress covers can best be compared to emptying the Atlantic Ocean with a teaspoon.

However, in the same article, allergy specialist Holger Mosbech recommended mattress covers and tried to argue that there was something wrong with our Cochrane review. This was a logical fallacy because, if he was right, this would not prove that mattress covers are effective. On our official website for patients, Mosbech continued recommending removal of carpets and using mattress covers.²¹

The Board of Health announced that they would look at the evidence again, not because of our Cochrane review, but because the Appeals Board had decided against them.

The Board said that there was no reason to change its advice about using mattress covers and “no need to doubt the Board of Health’s professionalism, or to doubt that the Board uses the best possible evidence.”²²

Monty Python’s Flying Circus would have been proud of our authorities. Instead of a Ministry of Silly Walks,²³ we should perhaps have a Ministry of Silly Advice.

The Board of Health never changed its recommendations. In 2018, they wrote that “improved asthma control may be achieved if house dust mite-reducing measures are used in the bedroom,”²⁴ quoting a 2015 guideline, which said that using allergen-proof mattress covers may reduce the patient’s contact with mite allergens.²⁵ In 2023, the Board claimed that exposure to house dust mites can be significantly reduced.²⁶

What decides what gets used in healthcare can be spelled with five characters: POWER or MONEY, which is about the same. In healthcare, the strength of the evidence has little power and many people are willing to accept even highly improbable claims.¹¹

References

1 Gøtzsche PC, Hammarquist C, Burr M. House dust mite control measures in the management of asthma: meta-analysis. BMJ 1998;317:1105-10.

2 Whitaker R, Cosgrove L. Psychiatry under the influence: institutional corruption, social injury, and prescriptions for reform. New York: Palgrave Macmillan; 2015.

3 Gøtzsche PC. Survival in an overmedicated world: look up the evidence yourself. Copenhagen: People’s Press; 2019, page 22.

4 Association of Certified Fraud Examiners. Fraud 101: What Is Fraud? (accessed 3 Jan 2024).

5 Gøtzsche PC, Johansen HK. House dust mite control measures for asthma. Cochrane Database Syst Rev 2008;2:CD001187.

6 Gøtzsche PC, Johansen HK. House dust mite control measures for asthma: systematic review. Allergy 2008;63:646–59.

7 National Heart, Lung, and Blood Institute; National Asthma Education and Prevention Program. Expert panel report 3: guidelines for the diagnosis and management of asthma. Washington, DC: US Department of Health, 2007.

8 Gøtzsche PC. Asthma guidelines on house dust mites are not evidence-based. Lancet 2007;370:2100–1 and Gøtzsche PC, Johansen HK. Authors’ reply on ‘House dust mite control measures for asthma’. Allergy 2009;64:190.

9 Bacharier LB, Boner A, Carlsen KH, et al. Diagnosis and treatment of asthma in childhood: a PRACTALL consensus report. Allergy 2008;63:5–34.

10 Mitka M. New evidence-based guidelines focus on treatment of children with asthma. JAMA 2008;299:1122-3.

11 26 Gøtzsche PC. Whistleblower in healthcare (autobiography). Copenhagen: Institute for Scientific Freedom 2025 (freely available).

12 Schmidt LM, Gøtzsche PC. Of mites and men: reference bias in narrative review articles; a systematic review. J Fam Pract 2005;54:334–8.

13 Pingitore G, Pinter E. Environmental interventions for mite-induced asthma: a journey between systematic reviews, contrasting evidence and clinical practice. Eur Ann Allergy Clin Immunol 2013;45:74-7.

14 Hallas HE. House-dust mites in our homes are a contamination from outdoor sources. Medical Hypotheses 2010;74:777–9.

15 Dust mite allergy. Mayo Clinic 2021:July 31.

16 Dust mites and asthma. Asthma + Lung UK 2023;Sept 30.

17 Andersen JB. Grotesk sagsbehandling og afgørelse i Ankestyrelsen: Den træffer afgørelser uden specialister og partshøring. Ugeskr Læger 2009;171:3219.

18 Gøtzsche PC. Evidensbaseret medicin: Ankestyrelsen mod Sundhedsstyrelsen om husstøvmider. Ugeskr Læger 2009;171:3727.

19 Andersen JB. Cochraneanalyse om støvmidebetræk er ikke evidensbaseret medicin. Ugeskr Læger 2010;172:651.

20 Hoffmann T. ”Husstøvmider bor ikke i madrassen.” Videnskab.dk 2010;June 28.

21 Mosbech H. Allergi for husstøvmider. Sundhed.dk 2022;June 2.

22 Smith E, Blands J. Svar fra Sundhedsstyrelsen om husstøvmider. Ugeskr Læger 2010;Mar 18.

23 Ministry of Silly Walks.

24 National klinisk retningslinje for non-farmakologisk behandling af astma hos børn og unge: Quick guide. Sundhedsstyrelsen 2018.

25 Non-farmakologisk behandling af astma hos børn og unge. Sundhedsstyrelsen 2015;Sept 23.

26 Astma hos børn. Rationel Farmakoterapi 2023;5;Oct 16.