Tea tree oil is an essential oil that owners often apply to their pet’s skin for a variety of reasons, the most common being as a flea repellent or to relieve the symptoms of a skin irritation. It is assumed that because it is a natural product they can use it with no adverse consequences. However, the topical application of even a few drops of oil can be toxic to both dogs and cats, especially if the preparation is a concentrated oil. This excludes commercially available toiletry or cosmetic products that contain tea tree oil in low concentrations.

The clinical signs normally start within 2-8 hours and vary in severity depending on the preparation and amount involved. The most common systemic effects (after ingestion or dermal exposure) include ataxia, depression, tremors, vomiting and hypersalivation. However in more severe cases the animal may present with paralysis of the hindlimbs, collapse or coma and occasionally these cases are fatal. The renal and liver parameters may also be raised.

If applied topically, treatment consists of thorough dermal decontamination by washing with detergent until the oily appearance of the skin has gone and the odour is reduced. In mild cases the signs will resolve quickly and the prognosis is good.

In more severe cases (if the animal does not recover or deteriorates) the animal should be monitored and receive supportive and symptomatic treatment. If very severe, the use of lipid infusion should be considered. The prognosis in these cases is more guarded.