In 1826 this tree was classified as a laurel, Laurus regia, by botanist David Douglas.

He discovered that inhalation of its fumes can lead to a painful cold sensation and severe headaches.

In earlier times the leaves of the tree were used for cures for headaches or stomachaches and even toothaches.

Umbellulone can cause severe headaches by activating transient receptor potential cation channel, subfamily A, member 1 (TRPA1) and influencing the trigeminovascular system via calcitonin gene-related peptide (CGRP).

Stimulation of these nerve fibers will eventually lead to the release of CGRP, a nociceptor known for its ability to induce migraine and cluster headache attacks.

The increase in immune cells and its inflammatory response is thought to be the main cause of the occurrence of migraine.

Still, the vasodilatory effect and the blood flow increase can be used as an indirect indication for the release of CGRP and therefore for the presence of the migraine and headaches.

Contact with the oil, or exposure to the vapors, can cause: Umbellulone induces rapid production of methemoglobine.

Red blood cells will be less able to nurture organs with oxygen, therefore, the probability for hypoxia increases.

Methemoglobin lethality is possible at concentrations higher than 50% of the substance in red blood cells.

Umbellularia californica should not be mistaken for the conventional bay leaf (Laurus nobilis), which is devoid of these toxic effects.