Q. Is Euphorbia tirucalli (Pencil cactus) harmful to dogs or cats?
Most of the information about the toxicity of the sap of Euphorbia tirucalli (Pencil cactus) is about humans, but it is just as toxic to your pets. When a pet bites into the plant, there will be immediate pain in the mouth. The plant is actually planted in gardens as a deterrent for wildlife. The stomach irritation caused by ingestion sometimes causes vomiting or diarrhea. Eyes will burn if the sap touches them and there are rare cases of temporary and permanent human blindness from contact. Dermal reactions can take awhile to show up, but painful rashes or blisters might occur.
Contact your vet if your pet has eye contact with the sap or if continuous vomiting might cause dehydration. Gently wash your pet's skin if the contact is dermal.