Placebo effects in allergen immunotherapy: an experts’ opinion


Placebo effects are common in medicine. Randomised clinical trials help us to understand their magnitude in different therapies. There are particular problems with placebo effects in allergen immunotherapy (AIT) as it is difficult to blind the active treatment and the endpoints are largely subjective. This may explain why large placebo effects are often found in AIT trials. Patients receiving open label AIT get the benefit of the active and placebo components but it can be difficult to say how much benefit is due to the active component. The use of active placebos has been proposed but brings its own problems (ethical and scientific). An EAACI Task Force has been established to address these issues. Here we review the current literature on the placebo effect in general, with a special focus on AIT trials, and indicate what we believe to be important considerations and unmet needs in AIT trial design.

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Allergen immunotherapy


Double-blind, placebo-controlled


European Academy of Allergy and Clinical Immunology


Quality of life


Subcutaneous immunotherapy


Sublingual immunotherapy


Synthetic peptide immunoregulatory epitopes


Task Force


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Corresponding author

Correspondence to Anthony J. Frew MD FRCP.

Additional information

*This article is based on a lecture given by the corresponding author at the 15th International Paul Ehrlich Seminar (September 6–9, 2017), Bad Homburg, Germany.

Conflict of interest

A.J. Frew has conducted clinical trials of subcutaneous and sublingual immunotherapy with several pharmaceutical companies including ALK-Abello, Allergopharma and Stallergenes but has no other current interests to report. O. Pfaar reports grants and personal fees from ALK-Abelló, grants and personal fees from Allergopharma, grants and personal fees from Stallergenes Greer, grants and personal fees from HAL Allergy Holding B.V./HAL Allergie GmbH, grants and personal fees from Bencard Allergie GmbH/Allergy Therapeutics, grants and personal fees from Lofarma, grants from Biomay, grants from Nuvo, grants from Circassia, grants and personal fees from Biotech Tools S.A., grants and personal fees from Laboratorios LETI/LETI Pharma, personal fees from Novartis Pharma, personal fees from MEDA Pharma, grants and personal fees from Anergis S.A., personal fees from Mobile Chamber Experts (a GA2LEN Partner), personal fees from Pohl-Boskamp, personal fees from Indoor Biotechnologies, grants from Glaxo Smith Kline, outside the submitted work.

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Frew AJ, Pfaar O. Placebo effects in allergen immunotherapy: an experts’ opinion. Allergo J Int 2018;27:162–6

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Frew, A.J., Pfaar, O. Placebo effects in allergen immunotherapy: an experts’ opinion. Allergo J 27, 31–35 (2018).

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  • sublingual
  • subcutaneous
  • clinical trials
  • endpoints
  • EAACI task force