Introduction
Allergic rhinitis causes symptoms such as sneezing, runny nose or itchy
eyes, which are especially prevalent in the pollen season1. Such symptoms of allergic rhinitis can be reduced
by some available medications; however, these medications often have
side effects, and the results from placebo-controlled clinical trials
suggest that symptom improvement is largely driven by the placebo
response 2-5. This raises the question of whether
allergic symptoms can be reduced by placebos, which usually do not have
any side effects. The placebo response is known to contribute to symptom
reduction in a variety of conditions, based on psychobiological
mechanisms such as expectations, learning, and patient-provider
interaction 6-8. It has been believed that placebo
effects are based on the patients’ false belief of receiving active
medication. In recent years, however, a growing body of research has
demonstrated that placebos being prescribed to patients with full
honesty and transparency (referred to as “open-label placebos” = OLPs)
improve symptoms in irritable bowel syndrome 9,10,
chronic back pain 11-13, migraine14, cancer-related fatigue 15,16,
depression 17,18, test anxiety 19,
and other conditions 20. With respect to allergic
rhinitis, though, there is inconclusive evidence regarding the
effectiveness of OLP.
In two small samples of people with allergic rhinitis, Schäfer et al.
found that OLP significantly reduced the frequency of allergic symptoms
in comparison to treatment as usual (TAU) 21,22. In
another study with a slightly larger sample size, OLP failed to improve
the severity of symptoms of allergic rhinitis 23.
These studies differed in two important respects. First, in the studies
by Schäfer et al., OLP was administered in a clinical encounter with
physical contact 21,22, whereas in the study by Kube
et al. 23, OLP had to be provided remotely (i.e.,
through a virtual encounter) due to the COVID-19 pandemic. The second
difference pertains to different measures used for the assessment of
allergic symptoms. While Schäfer et al. used a questionnaire assessing a
broad variety of allergic symptoms 21,22, Kube et al.
followed the recommendations of regulatory authorities24 to use a short scale that assesses only symptoms
related to eyes and nose 23. In addition, the two
measures differed in so far as the former assesses the frequency of
allergic symptoms, whereas the latter assesses symptom severity.
Drawing on that previous research, the present study sought to examine
the effects of OLP on symptoms of allergic rhinitis. Specifically, we
compared the effects of OLP plus TAU with TAU alone in a
randomized-controlled trial (RCT). The primary endpoint was symptoms of
allergic rhinitis. To address different assessment approaches as a
potential explanation of the discrepant results in previous research21-23, the current study applied both previously used
measures to assess both the severity and the frequency of allergic
symptoms. The secondary endpoint was the degree of impairment caused by
allergic symptoms. Based on the results of previous research23, we also examined whether the effects of OLP are
modulated by current anti-allergic medication.