Comments on the Retraction by PLoS ONE of a Laboratory Study on Arnica montana.

In June 2019, the journal PLoS ONE retracted an original research article, published in 2016, which described the effects of homeopathic on interleukin-4 treated human macrophages. The results showed an increase in extracellular matrix gene expression, including the gene encoding fibronectin, which is one of the main proteins involved in connective tissue healing. Here, the authors of the article discuss the critical points raised by the journal in the retraction note, with a focus on the specific methodological aspects of research on high dilutions of natural compounds. The editorial arguments made to justify the retraction did not prove any methodological errors, nor scientific misconduct. As a general rule, when a study published by a group of researchers raises scientific doubts because the results appear at variation with the commonly accepted knowledge in a field, the study is repeated by other scholars and any contrasting results are published and/or discussed. Therefore, retraction of the study by PLoS ONE is a violation of the conventions of scientific publication and knowledge-sharing methods derived from honest experimental method.