Calamus has been identified as an unsafe herb.

– Am J Health Syst Pharm 1999 Jan 15;56(2):125-38; quiz 139-41 — Unsafe and potentially safe herbal therapies. — Klepser TB, Klepser ME.

The preparation has quite diverse biological activity – tranquilizing, sedative, antiulcer, spasmolytic and antisclerosing. In its pharmacological properties the studied asarone is identical with asarone obtained from Acorus calamus and Guatteria.

– Farmakol Toksikol 1985 Nov-Dec;48(6):17-20 — Asarone and its biological properties — Belova LF, Alibekov SD, Baginskaia AI, Sokolov SIa, Pokrovskaia GV.

It was found that processing of herbs was associated with a very high pollution of the air with bacteria, fungi, dust and endotoxin. Reported as having allergenic and/or immunotoxic properties. The workers of herb processing plants could be exposed to large concentrations of airborne microorganisms, dust and endotoxin posing a risk of work-related respiratory disease.
– Ann Agric Environ Med 2001;8(2):201-11 — Exposure to airborne microorganisms and endotoxin in herb processing plants. — Dutkiewicz J, Krysinska-Traczyk E, Skorska C, Sitkowska J, Prazmo Z, Golec M.

Calamus may have a stimulating and hallucinogenic effect and may cause dizziness or nausea.

May be carcinogenic.