Tea Tree (Melaleuca Alternifolia) Essential Oil
Essential oil steam-distilled from the Australian tea tree, containing terpenes — primarily terpinen-4-ol. Marketed in pet shampoos and topical products for antimicrobial and anti-itch properties. But tea tree oil is a documented toxin in dogs and cats: the ASPCA Animal Poison Control Center and published case series report that even small volumes of concentrated oil, applied topically or ingested, cause depression, weakness, incoordination, tremors, and in severe cases require hospitalization. Cats are especially vulnerable because they can't efficiently metabolize the terpenes. Toxicity has been reported at concentrations that manufacturers still use in commercial products.
What it's doing there
Fragrance / antimicrobial agent.
The concern
Toxic to dogs and cats at low doses. A 2014 review of over 400 cases found the majority of poisonings resulted from products applied deliberately for therapeutic reasons, not accidental ingestion — meaning the exposure route is the product itself. High-risk in any leave-on or cat-accessible formulation.
How sure are we
High. This ingredient is well documented and there is broad agreement about how it behaves.
Note: ASPCA-documented toxin in dogs and cats; concentrated oil causes tremors and CNS depression, with cats at highest risk.
How this affects a score
In any product containing it, this ingredient lowers Ingredient Quality substantially, costs points under Potential Irritants, costs points under Fragrance Load. See the full formula →
Products containing Tea Tree (Melaleuca Alternifolia) Essential Oil
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This application is intended for educational purposes only. Scores are generated using publicly available product information and are not veterinary advice. We are not veterinarians. Always consult your veterinarian regarding medical decisions.
A high score does not mean a product is right for your pet, and a low score does not mean it is dangerous. An individual animal can react to an ingredient that scores well here, and a product with a mediocre score may be exactly what your vet recommends.
The score reads ingredients one at a time. It cannot account for how ingredients interact with each other, with other products you use, or with your pet's medications and conditions. Two ingredients that are each fine on their own may not be fine together. A score is a starting point for questions, not a substitute for professional judgment.