The spice nutmeg appears to have a relatively narrow margin of safety. Nutmeg can be fatally poisonous.
Certain natural constituents of spices such as nutmeg may form amphetamine compounds within the body, sufficient to elevate the mood and help provide some added Christmas cheer, during the holiday season.
This hypothetical risk was raised as far back as the Sixties in the New England Journal of Medicine in an article called "Nutmeg Intoxication." The paper pondered whether the age-old custom of adding nutmeg to eggnog arose from the psychopharmacological effects described in cases of nutmeg intoxication. Such cases evidently go back to the 1500s, when it was used as an abortifacient to induce a miscarriage and in the 1960s as a psychotropic drug.
Mental health professionals from the '60s concluded that while nutmeg is much cheaper for use and probably less dangerous than the habit-forming heroin, it must be stated that it is not free from danger and may cause death. The toxic dose of nutmeg is two to three teaspoons.
There are also potentially toxic compounds in certain types of cinnamon.