The principle of the use of leeches is associated with traditional medicine of many countries and its application has different philosophies for use in different areas of the body. Leeches, with all the benefits, can have dangers.

A review of complications of leech therapy was done based on English articles indexed in the databases up to July 1, 2018. A strategic search has done independently by members of the research team and then all of the articles were +categorized by subject.

Related articles were mostly case-reports. Complications were divided into five categories including infection, allergy, prolonged bleeding, migration, and others. Infection is the most-reported complication related to leech therapy and Aeromonas spp. has the most participation in infections.

Leech therapy can be a therapeutic complementary method if the possible complications are managed properly.