SOURCES

Citrus oil extracts, including d-limonene and linalool, are derived from citrus fruit skin. d-Limonene is a monocyclic terpene with insecticidal properties, especially from the vapor, which primarily acts as a desiccant.¹ d-Limonene is toxic to all life stages of the flea with the order of sensitivity from most to least being eggs, adults, larvae, and pupae.¹

Several products containing citrus oils are marketed to control ticks, fleas, and other insects. These products include insect sprays, pet dips, shampoos, and soaps. Solvents, fragrances, and cleansers are other types of products that may contain citrus oils.

TOXIC DOSE

In dogs the oral toxic dose of limonene is 680 g/kg; however, cats appear to be more sensitive than dogs.² A dermal study demonstrated that cats had clinical signs when a commercial pet dip containing 78.2% d-limonene was used at five times the recommended dose.³ In another study, three cats were dipped in a citrus product marketed for dogs. The product was diluted according to label directions, and one cat subsequently died. One cat became symptomatic but recovered, and one cat remained asymptomatic.⁴ A third study examined the use of a ready-to-use spray containing d-limonene, linalool, and piperonyl butoxide (a mixed function oxidase inhibitor). Mild signs appeared with a single dose in one of six cats.⁵ In one case report, a cat had severe clinical signs and was euthanized following the reportedly correct use of a 1% d-limonene-based shampoo labeled for dogs and cats.¹

TOXICOKINETICS

Citrus oils are absorbed rapidly both via the dermis and orally, and the distribution within the body is similar to that of other lipid-soluble compounds.² d-Limonene reaches maximum blood concentrations 10 minutes after dermal exposure.¹ The urinary tract is the main route of excretion, and less than 10% of excretion is by the fecal route.²