Ingestion of macadamia nuts by dogs has been associated with a nonfatal syndrome characterized by vomiting, ataxia, weakness, hyperthermia, and depression. Dogs are the only species in which signs have been reported.
Macadamia nuts are cultivated from Macadamia integrifolia in the continental USA and M tetraphylla in Hawaii and Australia. The mechanism of toxicity is not known. Dogs have shown signs after ingesting 2.4 g of nuts/kg body weight. Dogs experimentally dosed with commercially prepared macadamia nuts at 20 g/kg developed clinical signs within 12 hr and were clinically normal without treatment within 48 hr.
Within 12 hr of ingestion, dogs develop weakness, depression, vomiting, ataxia, tremors, and/or hyperthermia. Tremors may be secondary to muscle weakness. Macadamia nuts may be identified in vomitus or feces. Mild transient increases in serum triglycerides, lipases, and alkaline phosphatase were reported in some dogs experimentally dosed with macadamia nuts; these values quickly returned to baseline. Signs generally resolve within 12–48 hr.
For asymptomatic dogs with recent ingestion of more than 1–2 g/kg, emesis should be induced; activated charcoal may be of benefit with large ingestions. Fortunately, most symptomatic dogs recover without any specific treatment. Severely affected dogs may be given supportive treatment such as fluids, analgesics, or antipyretics.