Canine “scent training,” or “nose work,” in which dogs are coached to locate target-scented objects, may lead to accidental poisoning, researchers say. Faculty at the toxicology laboratory of the Diagnostic Center for Population and Animal Heath at the Michigan State University College of Veterinary Medicine say that targets scented with essential oils—specifically birch—create serious concern.
Cheryl Swenson, DVM, PhD, DACVP (clinical pathology), Angie Davison and John Buchweitz, PhD, recently confirmed that a highly toxic concentration of methyl salicylate is present in birch oil. The aromatic compound is reminiscent of wintergreen with a similar structure and toxicity profile to aspirin (acetylsalicylic acid). Clinical signs of possible birch oil toxicosis include a wintergreen smell coming from the pet (hair coat, skin, breath, vomitus), face rubbing, vomiting, diarrhea, gastrointestinal erosions, anemia, acute kidney failure, respiratory depression, lethargy, seizures, coma and death.
Birch oil, as well as anise and clove, are often used in canine scent training and are easily obtained from online sources. MSU researchers say that, typically, small amounts of these oils (diluted to 25 percent or less of their original concentration, per label instructions) are used in enclosed containers to reduce the chance of accidental ingestion. However, if dogs come across the bottle of undiluted product they may investigate it extensively, including by mouth, which may lead to oral ingestion as well as dermal absorption. Plus, many manufacturers emphasize the human health benefits of these oils on the label and downplay their toxicity, which may result in dog owners and handlers not taking proper precautions.
In addition to the toxicity of these oils, there is also potential for dogs to target items of a similar scent that are also toxic. Researchers found that birch scent is frequently incorporated into sugar-free chewing gum, which often contains xylitol, a compound that is safe for human consumption but toxic to dogs.
“In fact, all three commonly used training scents have been incorporated into chewing gums and thereby may promote the unanticipated risk of xylitol poisoning,” the researchers state in their report. “Therefore, it is recommended that alternative nontoxic scents be actively sought to ensure safety for people and pets during the enjoyable human-animal bond activity of training dogs to locate odors.”
MSU researchers recommend that pet owners and trainers working with scent training use floral or other scents that don’t encourage dogs to seek food sources with similar odors. They recommend that owners and trainers identify safe scents by making sure the plant form of the scent is not poisonous and that candidate scents are tested to rule out the presence of unanticipated toxins.