Discussion
The present results show that although OLP did not significantly improve
the severity of allergic symptoms in comparison to TAU, it did reduce
the frequency of symptoms and the degree of allergy-related impairment.
By distinguishing between symptom severity and symptom frequency, the
current results can resolve the inconclusive findings from previous
research on the effects of OLP in allergic rhinitis: Previous studies
revealing a significant effect of OLP assessed symptom frequency only21,22, whereas a previous study that failed to find a
significant effect of OLP over TAU focused only on symptom severity23. Assessing both symptom severity and frequency, the
present results suggest that OLP has medium to large effects on the
frequency of allergic symptoms, whereas its effects on symptom severity
are only small to medium (which failed to reach significance in the
present study, possibly due to insufficient power to uncover such
effects).
An altnernative interpretation of the discrepant results for the two
symptom measures might be the breadth of symptoms being considered. More
specifically, the symptom severity measure focuses on allergic symptoms
related only to the nose and eyes, whereas the frequency questionnaire
also considers additional symptoms. Indeed, the analysis of more
specific symptom clusters suggests that the beneficial effects of OLP
over TAU were particularly pronounced in symptoms pertaining to the
eyes, breathing, and more general symptoms such as tiredness or trouble
concentrating, whereas the majority of the items of the CSMS refers to
nose-related symptoms. Thus, it might be that the CSMS is not ideal to
capture the beneficial effects of OLP on the variety of allergic
symptoms.
With regard to symptom-related impairment, it is worth noting that the
present study, unlike previous studies 21-23, found
that OLP significantly reduced impairment, with medium to large effects.
Possibly, this is related to the fact that the present study, unlike
previous work, used a questionnaire that assesses impairment
specifically in the context of allergic symptoms. Thus, combining the
present findings with prior research 21-23, it seems
that OLP has the potential to reduce allergy-specific impairment, but
not impairment more generally.
Given the positive results regarding the reduction of symptom frequency
and impairment through OLP, the current findings suggest that a physical
patient-provider interaction might not be necessary for OLP to work.
This is an important finding with respect to the still ongoing COVID-19
pandemic and its restrictions of physical contact as well as increasing
demand for online therapy. Taking the less positive results of a
previous study administering OLP remotely into account23, it may be important to make sure that patients can
start taking the placebos immediately after the virtual encounter, as it
was done in the present study. In line with that notion, participants
from the TAU group who started taking placebos with a few days delay did
not show that much improvement as well. In addition, the correlational
results suggest that it is important to ensure that patients are
properly informed about the effects of OLP, since the extent to which
participants felt informed about placebos was associated with lower
symptom burden after taking OLP.
Limitations
The most significant limitation of the present study is its relatively
low sample size. Althought the current sample size was larger than in
all previous studies examining OLP in allergic rhinitis21-23, it did not offer enough power to uncover small
to medium effects, as it would have been necessary for the effects of
OLP on symptom severity. Furthermore, the current study focused on
self-reported allergic symptoms only, and future research may examine
whether beneficial effects of OLP can also be observed on a
physiological or immunological level.
Conclusions
The present results suggest that remotely provided OLP can improve the
frequency of allergic symptoms as well as allergy-related impairment
over TAU. OLP might also have beneficial effects on symptom severity,
but this effect warrants further exploration using larger samples.