The Cochrane Collaboration conducted a meta-analysis of clinical trials studying the effect of orally administered EPO on eczema and concluded that there was no effect. The Mayo Clinic examined evidence for the safety and effectiveness of evening primrose for several conditions; it was considered that there was "good evidence" (grade B, vs "strong evidence", grade A) that it produced a moderate improvement in eczema. Grade C, "unclear", evidence for benefit is listed for other conditions. Research has shown a lack of significant beneficial effects on heart functions. Many conditions for which evening primrose oil is a traditional remedy or there is a theory suggesting efficacy are listed by the Mayo Clinic without comment.