Yes, macadamia nuts are toxic to dogs. Even small amounts of macadamia nuts can make your dog sick. These nuts contain an unknown toxin that can affect a dog’s health. Symptoms of macadamia nut toxicity in dogs may include vomiting, hyperthermia, lethargy, tremors, and muscle stiffness. If you suspect that your dog has ingested macadamia nuts or exhibits any signs of illness, it's important to contact your veterinarian right away. They can help you determine the appropriate treatment and steps to take to help your dog recover.