Study design, interventions, and procedure
allergic symptoms, allergic, OLP
ALLERGIC RHINITIS
The study design consists of a randomized placebo-controlled four-arm study of the OLP-treatment and its effects on symptoms of allergic rhinitis. The OLP treatment was compared to a conventional double-blind placebo arm, a TAU control arm, and a double-blind drug condition (probiotic treatment, PROB) (see Fig. We used drops for both placebo conditions (OLP and double-blind placebo) that included the carrier solution of the probiotic treatment (lactose-monohydrate, glucose-monohydrate). The drops were indistinguishable in color, smell, and taste from the probiotic.The study was announced as research about psychophysiological interactions during the treatment of seasonal allergic symptoms. Participants were informed that they were assigned to different groups to receive a probiotic treatment or a placebo in a double-blinded fashion, or OLP, or no treatment. The probiotic treatment was offered to all participants after the end of the trial.All participants received the same information and instructions (no additional information, e.g., for OLP or PROB group, after group assignment). After signing informed consent patients first completed questionnaires to measure the allergic symptoms (see below). Subsequently all participants were told that placebos are inactive substances containing no medications, but that both deceptive as well as non-deceptive placebos may still be powerful. We further explained that a possible mechanism for placebo responses may be classical conditioning, that a positive attitude may be helpful, but is not necessary, and that taking placebos faithfully is important. This information was analogue to previous studiesIn the DBP and OLP condition participants were instructed to take 30 drops three times a day. OLP or DBP (or PROB) groups received no further instruction or information. All participants were asked to complete a daily diary about the burden of allergic symptoms.After 4 weeks all participants were invited for a second visit with a blinded experimenter, in which participants completed again questionnaires with respect to the allergic burden.