Red snow: is it safe to eat? A pilot study

The objective of this study was to determine if the ingestion of snow contaminated with Chlamydomonas nivalis causes diarrhea. The design was a single-blind crossover. Subjects were seven healthy volunteers, aged 24-56 who ingested 500 g of snow contaminated with C. nivalis. Outcome was measured by stool and diarrhea frequency. No differences in stool or diarrhea frequency were noted between treatment and placebo groups. The conclusion is that in this pilot study, there was no evidence supporting the concern that ingestion of "red snow" causes diarrhea.