About 20 different species of deciduous trees in the Juglan genus are collectively labeled as walnuts. Six of those species are native to the United States. Walnut wood has a deep, rich, chocolate color that's highly prized by some woodworkers. The wood is used to produce furniture, flooring, interior moldings and wood turnings. Walnut is also used to make salad and serving bowls.
Some people and animals have allergic reactions to wood chips and sawdust from walnut trees. Allergic reactions unrelated to the wood -- from pollen as well as from the fruit of walnut trees -- are more common. Black walnut and butternut trees produce a chemical that's toxic to other plant life.
The roots of walnut trees produce a toxin called juglone, according to the Ohio State University Extension. While juglone is found throughout these trees, as well as in the wood itself, the root structure holds the chemical in very high concentrations. Juglone may be the culprit behind allergic reactions in humans exposed to walnut sawdust or wood chips.
Allelopathy describes the toxic effects of one plant species upon another, according to the West Virginia University Extension Service. It was first reported by a Roman natural scientist, Pliny the Elder, in 77 AD. Walnuts generate juglone as a means of killing off certain competitive plant and tree species within a 50- to 60-foot radius of the trunk, according to the Ohio State University Extension.
Allergies and Sensitivities
Irritations to the skin, eyes, nose, throat and lungs occur in some people exposed to wood or sawdust from walnut. Allergies and asthma may also be stimulated by exposure. The problems are not widespread, but using dust masks when working with walnut is advisable as a precautionary measure.
Many people develop allergies to nuts, including walnuts. However, there doesn't appear to be any direct correlation between allergies to walnut fruit and allergies to the wood itself.
Other Health Claims
According to the American Cancer Society, black walnut is promoted as a natural remedy for a number of illnesses including "acne, thyroid disease, colitis, eczema, hemorrhoids, ringworm, sore throats, tonsillitis, skin irritations and wounds." Most of the claims involve use of walnut hulls, teas made from walnut leaves and infusions derived from the inner bark of the tree. However, the American Cancer Society also notes that "Available scientific evidence does not support claims that black walnut hulls, bark, or leaves can cure or prevent any disease, including cancer." But, the group does say that a few laboratory tests have shown that juglone may have some antitumor properties.
- Photo Credit wooden walnut puzzle unassembled image by Robert Yoder from Fotolia.com
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