Peppermint oil

What is peppermint oil?

Peppermint oil is steam-distilled from Mentha piperita, with menthol typically the dominant constituent alongside menthone, menthyl acetate and smaller amounts of other monoterpenes. Composition varies substantially with cultivar, growing conditions and harvest timing, which means "peppermint oil" is a variable material rather than a defined chemical.

How does peppermint oil work?

Contact activity through disruption of insect and mite cuticle and membranes, plus a repellent and antifeedant effect attributed to interference with octopamine receptors - an invertebrate neurotransmitter system with no mammalian equivalent, which is part of why selectivity toward invertebrates is reasonable. Menthol also has vapour activity, contributing a repellent effect beyond the treated surface.

What does peppermint oil not do?

Highly volatile, so persistence is measured in hours to a day or two rather than weeks - repellency fades quickly. Not systemic. Not effective against armoured or well-protected pests such as mature scale. And at higher concentrations it is phytotoxic, particularly on young or stressed foliage in bright warm conditions.

Is peppermint oil safe?

Peppermint oil is toxic to cats for the same reason geraniol is: cats lack adequate glucuronyl transferase activity to conjugate and excrete terpenoid and phenolic compounds. Exposure routes include skin, inhalation and grooming, so no on-animal use, and treated areas should be dry and ventilated before access. This applies with particular force to Vetpure Miticide, which is an animal-premise product built on essential-oil actives.

Toxic to fish at low concentrations. Concentrated oil is a skin and mucous-membrane irritant, and menthol vapour is an airway irritant in enclosed spaces.

Products containing it

Spider Mite Control (with geraniol 30%, cottonseed and rosemary oils) and, per internal formulation notes, Vetpure Miticide in the Biosecurity range.