Well it seems it can according to this latest study on patients with allergic rhinitis and skin disorders (hives, itching, soreness).
Even though people knew they were taking a placebo and the pills were labelled as such, symptoms improved within a few days. It didn’t seem to matter either whether they were educated about how placebos work or not, or what their expectations were.
I do note that pollen counts dropped between the sessions so you would expect some improvement, but at least the researchers acknowledge that and took it into account, believing there was still a significant difference between active and control groups. They conclude:
Several trials have demonstrated that placebo without concealment can reduce symptoms in attention-deficit/hyperactivity disorder (ADHD), major depression, and neurosis.1-3 Results of this study suggest that allergic rhinitis can be added to these conditions.
Fascinating. The power of the mind…