red cedar
Meaning of red cedar: Not a cedar at all but a juniper, and the name is shared with an unrelated timber tree whose dust causes asthma.
Definition of red cedar
Red cedar is a common name for two different evergreen trees of the cypress family. Eastern red cedar, Juniperus virginiana, is a juniper whose fragrant heartwood yields cedarwood oil, used in soaps, perfume, aromatherapy and insect repellents. Western red cedar, Thuja plicata, is a separate species valued as timber and well known for the asthma its dust causes in woodworkers.
Which tree is meant?
| Common name | Species | What it really is | Health relevance |
|---|---|---|---|
| Eastern red cedar | Juniperus virginiana | A juniper | Source of cedarwood oil; pollen allergy |
| Western red cedar | Thuja plicata | An arborvitae | Occupational asthma from sawdust |
| True cedar | Cedrus species | A relative of the pines | A different oil, from a different family |
None of the trees sold as red cedar is a true cedar. Those grow in the Mediterranean and the Himalaya and belong to the pine family, while both American trees belong to the cypress family. The confusion is old, dates from settlers naming unfamiliar trees after familiar ones, and it matters because the two American species have entirely different effects on health.
What is the oil used for?
Cedarwood oil is steam distilled from the heartwood and sold as a fragrance for soap and perfume, as a moth deterrent for closets and chests, and as an ingredient in insect repellents. It appears in aromatherapy preparations marketed for calm and sleep, claims resting on small studies rather than on established evidence, and it served for many years as the immersion fluid placed between a microscope lens and the slide. Preparations labeled cedarwood may come from any of several species, so the label names an aroma more reliably than it names a plant.
What are the health effects?
Dust from Western red cedar is one of the best-documented causes of asthma acquired at work. A compound in the wood provokes a reaction in a minority of exposed sawmill and joinery workers, and the wheeze and cough can persist for years after exposure stops. Pollen from junipers of this group is a recognized seasonal allergen in parts of North America, producing streaming eyes and blocked noses in winter. The essential oil is concentrated, can irritate skin and provoke allergic rashes, and is harmful if swallowed, as is true of tea tree and other essential oils.
Also known as
Used in a sentence
The joiner's asthma was attributed to prolonged exposure to red cedar dust.
Good to know
Eastern red cedar and Western red cedar are different species with different consequences, one supplying an aromatic oil and the other a well-recognized cause of asthma acquired at work, and neither belongs to the true cedars.