Essential oils can possess antimicrobial, insecticidal, and anti-inflammatory properties. Their newfound celebrity as flea
preventives is bringing to light the differences in oversight of their efficacy and safety. Unlike with most veterinary-formulated
synthetic insecticide flea control products, the Environmental Protection Agency (EPA) has no registration or regulatory control
over plant-derived natural flea products containing essential oils. This exemption has led to a boom in the development and
sales of many essential oil-containing topical flea products ranging from shampoos and sprays to spot-on formulations.
GETTY IMAGES / ANGELA SORRENTINO
Measuring the effects
In an attempt to describe the adverse effects of exposure to these products in dogs and cats, researchers at the University
of Illinois at Urbana reviewed electronic medical records obtained from the ASPCA's Animal Poison Control Center. They evaluated
all reports of known exposure of dogs and cats to natural flea preventives, which included nine dogs and 39 cats. For all
the dogs and cats, the frequency, types of reactions, time until onset, and duration of signs were noted. The researchers
also recorded whether the products were applied according to label recommendations and the final outcome and treatment information.
Adverse effects were seen in 92% of the cats and 89% of the dogs. The remaining animals did not experience adverse events
or develop clinical signs related to the exposure, but these cases were referred to the ASPCA APCC because the product was
not used correctly or because more than one animal in a household was exposed but only one developed clinical signs.
Signs included behavior changes and central nervous system, gastrointestinal, and respiratory effects. There were, however,
some obvious species differences. Cats appear to be more sensitive, and behavior changes were more commonly reported in this
species. Also, of the central nervous system signs reported, dogs tended to experience lethargy, while seizures and tremors
were reported more frequently in cats. These findings are consistent with those described in the literature on essential oil
In 77% of the reports the products were used appropriately, eliminating improper application as the only cause of adverse
events. The onset of signs was generally within 24 hours of exposure, and the duration of the effects ranged from 30 minutes
to just over six days. Most of the animals recovered with dermal decontamination through bathing alone. Others required more
substantial therapy, including intravenous fluids, muscle relaxants, and anticonvulsive medications. Three animals either
died or were euthanized as a result of intractable clinical signs.
Flea products that contain essential oils, defined as "minimum risk pesticides" by the EPA, can cause serious adverse effects
in dogs and cats, even when applied according to label instructions. In this case series from the APCC, most of the patients
exposed to the plant-derived natural flea products were symptomatic. Spot-on products were used most frequently.
There are still many unknowns regarding the safety of these products. As the authors of this study indicate, the quality control
of essential oil flea products is not currently regulated or monitored, and possible interactions between the essential oils
themselves and other chemicals that could affect absorption are not known. Additionally, various health and other dermal conditions
could alter the absorption of these products, making toxicosis more likely. Until more data and oversight of these products
are available, caution owners to use them with care.
Genovese AG, McLean MK, Kahn SA. Adverse reactions from essential oil-containing natural flea products exempted from Environmental
Protection Agency regulations in dogs and cats. J Vet Emerg Crit Care 2012;22(4):470-475.