Toxicoses From Essential Oils in Animals

Essential oils are readily and rapidly absorbed through the GI tract, skin, lungs, and mucous membranes. Systemic absorption should be expected, and multiple signs of essential oil toxicosis can develop. The higher the concentration of essential oil, the greater the risk to the animal. Concentrated essential oils should never be directly applied to pets.

Although both dogs and cats can be affected by essential oils, cats are more sensitive because they are deficient in the enzyme glucuronyl transferase. This enzymatic deficiency makes cats very sensitive to phenol and phenolic compounds, which some oils contain. Cats’ natural grooming behavior places them at additional risk from both dermal and oral exposures.

Dogs do not have the same enzyme deficiency as cats; however, they are still at risk for toxicosis from exposure to essential oils.

Birds are at high risk to be harmed, because their unique respiratory tract makes them particularly sensitive to fragrances and aerosolized particles. Inhalation of essential oils is also hazardous for any animals that have preexisting respiratory problems, such as the following:

• feline asthma

• airborne allergies

• chronic bronchitis

• chronic exposure to secondhand smoke

Essential oils can become contaminated by bacteria, posing additional threats from airborne bacterial infections. Cases of melioidosis occurred in the US in 2021 as a result of inhalation exposure to contaminated essential oils (1).

The diffusion method (passive or active) can influence the routes of exposure to essential oils:

• Passive diffusers (eg, reed diffuser, candle) do not emit actual droplets of oil, so unless the diffuser is tipped over, the main hazard to animals is respiratory irritation.

• Active diffusers (eg, nebulizing or ultrasonic diffusers) emit microdroplets or particles of oil into the air. Active diffusers pose an extra risk beyond inhalation exposure, especially for cats and birds. Microdroplets can collect on hair or feathers if the pet is in the same room as the active diffuser. The oil can then be either absorbed directly through the skin or ingested during self-grooming.

Clinical signs of essential oil toxicosis depend on the type and concentration of the oil, as well as on the exposure route. Signs develop within minutes to hours from all routes. The most common signs from ingestion or dermal exposure include vomiting, lethargy, drooling, ataxia, and anorexia. Other possible signs include tremors, hypotension, GI ulcers, bradycardia, hypothermia, seizures, rear-limb paralysis, skin irritation, liver failure, and kidney failure.

Clinical signs from inhalation exposure include lacrimation, watery nasal discharge, nausea, drooling, vomiting, dyspnea, tachypnea, coughing, or wheezing.

The following essential oils are potentially hepatotoxic:

• birch tar

• cassia bark

• cinnamon oil

• pennyroyal

• tea tree/melaleuca

Essential oils that can cause seizures include the following:

• birch

• cedar

• eucalyptus

• hyssop

• pennyroyal

• sage

• wintergreen

• wormwood

In addition, exposure to wintergreen and birch oils can produce aspirin toxicosis because they contain high levels of methyl salicylate (a form of aspirin).

• History

• Physical examination findings: aroma of essential oils

In general, diagnosis of essential oil toxicosis is based on reported use by the owner. The scent of essential oils on the patient's body or in vomitus might prompt a veterinarian to specifically ask about this possibility.

As with any intoxication, a CBC and serum chemistry panel are indicated diagnostic tests. In addition, coagulation profiles and serial blood glucose testing might be appropriate in patients with hepatic insufficiency. Thoracic radiography should be performed whenever respiratory exposure is reported or when abnormal respiratory signs are observed.

• Supportive care

• Removal of toxic substance

Toxicoses brought on by essential oils are treated with supportive care—fluid therapy, GI medications, hepatoprotectants (S-adenosylmethionine [SAMe]; N-acetylcysteine), anticonvulsants, oxygen, bronchodilators, steroids, antimicrobials—until clinical signs resolve. If possible, the patient should be decontaminated via bathing or exposure to fresh air. Because of the risk of aspiration, emesis should not be induced.

Veterinary professionals should advise pet owners of the following guidelines to prevent toxicoses from essential oils:

• Do not apply concentrated essential oils directly to pets.

• Avoid using essential oils that are known to be toxic.

• Prevent ingestion.

• Keep pets out of a room while using a diffuser, and ventilate the room afterward.

• Run diffusers for only short periods (< 30 minutes).

• Use diluted rather than concentrated oils.

• Khan SA, McLean MK, Slater MR. Concentrated tea tree oil toxicosis in dogs and cats: 443 cases (2002–2012). J Am Vet Med Assoc. 2014;244(1):95-99.

• Genovese AG, McLean MK, Khan 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.

• Also see pet owner content regarding household hazards.

1. Gee JE, Bower WA, Kunkel A, et al. Multistate outbreak of melioidosis associated with imported aromatherapy spray. N Engl J Med. 2022;386(9):861-868. doi:10.1056/NEJMoa2116130