Rosacea is also linked to the stomach bacteria, H. pylori. I had rosacea when I had H. pylori. Once the infection was treated, the rosacea cleared up and never returned (this was 12 years ago). I'm sure not all cases of rosacea are due to having H.pylori, but there is a link.
http://www.ncbi.nlm.nih.gov/pubmed/25653855

H.pylori has also been linked with affecting sinemet's absorption, and with worsening or motor symptoms in PD.
http://www.ncbi.nlm.nih.gov/pubmed/25560322

If you have rosacea, you may want to be tested for H. Pylori.