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I am sorry about the length of this reply, (which doesn't answer your question), but thought this information would be useful to have in this forum/archive. Especially, where one develops an allergy to one kind of wood, this should help predict what others woods might cause a similar reaction.
This research is specific to wood dust and not the actual skin contact with wood. Wood dust produces an extremely large amount of surface area, which has the potential produce much more extreme reactions than exposure to the amount of surface area that is in contact with the skin.
Only 2% to 5% of the population will develop an allergic sensitivity to one or more compounds found in wood. Contact dermatitis from timbers is usually attributable to contamination of the skin during machining. Handling of solid wood rarely induces dermatitis, however any species that contains quinones, especially Dalbergia species, may do so. (Calnan 1972). 1
Interestingly, most research seems to be reported based on only a few case studies, many of which go back up to 100 years and these results are not obtained by clinical studies with large sample groups. However, these isolated cases should not be dismissed; they are very interesting in showing patterns of cross-sensitivities, and many have been accompanied by positive patch tests from extracts of the offending compounds.
“The structural components of wood are cellulose, hemicellulose, and lignin, but it is the accessory substances or “extractives” found mainly in the heartwood that are responsible for most toxic effects. Vorreiter (1949/1958 ) classifies these as follows: (1) fats, resins, oils, and waxes ; (2) proteins, gums, latex, mucus, starch, and sugers ; (3) alkaloids, bitter principles, dyes, tannins, glycosides, camphor, perfumes, etc.; (4) inorganic and organic acids and salts ; (5) minerals.” 1
“Some of these act as food reserves for latent growth periods, some as hardening agents, and others protect against mechanical injuries or attack by bacteria, fungi, insects and larger animals (Dietrichs, 1958). Some are metabolic by-products or end-products of no apparent use to the tree.”
Toxic Substances
Quinones
The culprit behind these allergies is a group of chemicals called quinones, naturally occurring compounds, often used to make dyes. The quinones are produced as defensive agents against fungal and predator attacks (including me, the woodworker and you, the collector). Quinones play a major role in allergic contact dermatitis caused by plants.
The primary allergens are benzoquinones or naphthoquinones but also compounds, such as catechols, coumarins, and other phenolic or flavonoid compounds, which are bioconverted into ortho-quinones or para-quinones. Catechol is a main constituent of urushiol, which is the allergen in poison ivy. 2
It is possible that once sensitized to one of these quinones that cross reactions to similar quinones and/or structures can develop.
Other compounds
Some of the other compounds that are known to cause harmful responses include: alkaloids and glycosides (systemic effects, pharmacological rather than allergic), saponins (effective through broken skin only), phenols (the strongest skin-sensitizers, especially the catechols of the poison-ivy family), stilbenes (which occur in allergenic woods, but only chlorophorin and coniferyl benzoate are known to sensitize), terpenes (including delta-3-carene from turpentine, sesquiterpene lactones and other sensitizing liverworts found on bark, and euphorbol and other complex terpenes on uncertain toxicity found in the latex of Euphorbiaceae), furocoumarins (photosensitizing and may be partly responsible for skin reactions but has yet to be proved), and dalbergiones (severe skin irritants).
Toxicity
The hazardous forms that may give rise to health risks are:
“The main effect is irritation. An irritant is something that can cause inflammation or irritation. This can be caused by skin contact with the wood, its dust, its bark, its sap, or even lichens growing on the bark. Irritation can, in some species of wood, lead to nettle rashes or irritant dermatitis. These effects tend to appear on the forearm, backs of the hands, the face (particularly eyelids) neck, scalp and the genitals. On average, they take 15 days to develop, but have been known to occur in a few hours to many months. Symptoms usually only persist as long as the affected skin site remains in contact with the source of irritation. Symptoms subside when contact with the irritant is removed.
Sensitization dermatitis is more problematic and is usually caused by skin exposure to fine wood dust of certain species. Sensitization is an allergic reaction to a substance which is usually irreversible. Resulting in hypersensitivity and susceptibity to being overly responsive. This is also referred to as allergic contact dermatitis and results in similar skin effects to those produced by skin irritants. Once sensitized, the body sets up an allergic reaction, and the skin may react severely if subsequently exposed to very small amounts of the wood dust. Cross-sensitization may develop where other woods or even non-wood materials produce a similar response.” 3
Allergic Contact Dermatitis
An allergy is basically the negative health effects which result from the stimulation of specific immune responses. Allergic contact dermatitis is a form of delayed-type hypersensitivity reaction which is dependant upon cell-mediated immune function and the activity of T lymphocytes. The most frequent form of allergic reaction is to small molecular weight materials such as chemicals and proteins. These reactions are better known as contact hypersensitivity, skin sensitization, and allergic contact dermatitis.
This occurs in 2 stages:
Stage I (Induction Phase): Initial contact may result in the allergen penetrating the stratified squamous epithelial cells of the skin and binding to large dendritic (branched) white blood cells in the epidermis called Langerhans cells. The Langerhans cell (with the allergen on its membrane) migrates to a nearby lymph node where special white blood cells, called effector T-cells, are programmed to recognize the allergen. There are literally millions of effector T-cells roaming throughout the blood and lymphatic system, each with special receptor molecules on their membranes for a particular allergenic chemical. T-cells patrol our circulatory system looking for invading cells and viruses. 2
Stage II (Elicitation Phase): If you come in contact with the offending allergen during a subsequent encounter, an effector T-cell may encounter it bound to a Langerhans cell and attach to it by a complicated and specific recognition system. The effector T-cell then produces multiple clones and releases special proteins called lymphokines which attract a legion of different white blood cells, including macrophages and cytotoxic ("killer") T-cells. The new army of white blood cells releases cytokines or proteins which destroy everything in the vicinity including other skin cells, thus producing a blistering rash. 2
Milder effects range from redness (vasodilation) and itching (nerve injury) to small blisters (vesicles and bullae). Stronger effects can result in Anaphylaxis, which can occur in response to any allergen, while Anaphylaxis occurs infrequently; it is life-threatening and can occur at any time. Risks include prior history of any type of allergic reaction.
Here is a small list of popular woods that should be avoided.
Most of this information is taken from
Botanical Dermatology: Plants and Plant Products Injurious to the Skin.
Dalbergia spp (Rosewoods) With “the discovery of sensitizing quinones in other woods such as teak…led Schulz and Dietrichs (1962) to look for similar substances in Dalbergia nigra and Dalbergia retusa. They found three quinones which they called Dalbergia quinones A, B and C, and demonstrated by patch tests on patients that these were the sensitizers, the strongest being R-3,4-dimethoxydalbergione… They have now been found in most other Dalbergia spp.”
Dalbergia retusa (Cocobolo) contains S-4'-hydroxy-4-methoxy dalbergione, R-4-methoxy dalbergione and other quinones and phenols.
Dalbergia cultrate (Burmese Rosewood) contains a dalbergione.
Dalbergia nigra (Brazilian Rosewood) contains R-4-methoxydalbergione and other quinones.
Dalbergia latifolia (East Indian Rosewood, Sonokoling) contain R-4-methoxydalbergione and other quinones.
Dalbergia cochinchinensis (Laos Rosewood, Thai Rosewood, Cochin Rosewood) contain R-4-methoxydalbergione and other quinones.
Dalbergia stevensonii (Honduran Rosewood, Nagaed Wood, Palissandre Honduras) contains a dalbergione.
Dalbergia decipularis (Tulipwood) contains a dalbergione.
Dalbergia frutescens (Tulipwood) contains a dalbergione.
Dalbergia. melanoxylon (African Blackwood) contains several quinones including S-4'-hydroxy-4-methoxydalbergione and S-4-methoxydalbergione.
Dalbergia cearensis (Kingwood, de Violette, Violet Wood, Violetta) contains a dalbergione, described as a very severe skin irritant, often leading to persistent ulceration.
Dalbergia congestiflora (Mexican Kingwood) contains a dalbergione.
Dalbergia maritime (Madagascar Rosewood, Bois de Rose) contains a dalbergione.
Cordia dodecandra (Zericote, Ziricote) Cross reactions are possible with this species once sensitivity to R-3,4-dimethoxydalbergione (found in pao ferro and Dalbergia species), obtusaquinone (found in cocobolo), and macassar quinone (found in macassar ebony) have developed.
Cordia elaeagnoides (Bocote, Becote) Cross reactions are possible with this species once sensitivity to R-3,4-dimethoxydalbergione (found in pao ferro and Dalbergia species), obtusaquinone (found in cocobolo), and macassar quinone (found in macassar ebony) have developed.
Peltogyne densiflora (Purpleheart) “Dalbergiones have been isolated from the wood.”
Tetraclinis articulata (Thuya Burl) The heartwood of this species is known to contain several dermatologically active compounds including thymoquinone, carvacrol, and ß- and ?-thujaplicins.
Tectona grandis (Teak) The “dermatic compounds” (sensitizers) lapachol (aka tecomin, a quinone), desoxylapachol, and lapachonole (aka lapachonone) where found in Tectona wood. Lapachol has been called “a known elicitor of contact dermatitis” and a “sensitizing agent.” “Deoxylapachol and lapachenole…are potent contact allergens.” “Local races of teak and even individual trees vary greatly in desoxylapachol content.” “Lapachenole has been shown to be both irritant and sensitizing” by Sandermann & Barghoorn (1955). “Indonesian natives have long distinguished three grades of the wood, the poorest (Djati sempoerna) being liable to cause skin irritation”
Pterocarpus soyauxii (Padauk) can cause irritation of the skin, dermatitis, and sensitizer. Can have naphthoquinones. Cross-sensitivity may occur with use of Bocote when sensitivity has been developed to related quinones.
Machaerium scleroxylon (Pau Ferro) has dalbergiones. It can cause dermatitis, itching, swelling, redness of face, scrotum, and hands.
Guibourtia tessmannii (Bubinga) “Dermatitis, possibly caused by sensitizing quinones.”
Diospyros celebica (Macassar Ebony) contains macassar II, a ß-naphthol “derivative that may become oxidised in vivo to macassar quinone. This compound has been shown to have sensitizing properties in guinea pigs. Cross-sensitivity to other naphthoquinones” three found in zericote, pao ferro, cocobolo, becote, and padauk are possible. “Later testing confirmed sensitivity to R-3,4-dimethoxydalbergione (found in pao ferro), obtusaquinone (found in cocobolo), and macassar quinone (found in macassar ebony).” Wood of this specie is one of the only ones that these substances have been proven to be found in. “The yellow naphthoquinone pigment, plumbagin (methyl juglone) occurs in a colourless combined form and is liberated from root tissue by acid treatment. (Harborne 1966)… Plumbagin is also found in some species of the families Droseraceae, Ebenaceae, and Euphorbiaceae (Thomson 1971)…. Plumbagin has an irritating odor and causes sneezing; it stains the skin to a purple color and has a vesicant action.”
Cinnamomum camphora (Camphorwood) The wood contains camphor and borneol. Following cases of serious toxicity and even death in children, products containing more than trace quantities of camphor have now largely been withdrawn from the market (Reynolds 1996). “Can cause dermatitis and shortness of breath” and camphor causes mild heart stimulant activity. Topically applied, it can penetrate the skin.
Milletia laurentii (Wenge) can have central nervous system effects, give dermatitis, irritate skin, is listed as a sensitizer, and is oily.
Acer saccharum (Sugar Maple) “This species has been found to contain 2,6-dimethoxy-1,4-benzoquinone which is a known contact allergen”
Salix spp (Willow) contains salicin, a phenolic glucoside, and is a precursor of aspirin, also has saligenin, a known contact allergen. Willow is also listed as a sensitizer.
Betula spp (Birch) contain salicylates such as methyl salicylate, Cross-sensitivities could occur in those with aspirin allergies. Birch also listed as sensitizer.
Dymondwood is a manufactured wood product consisting of layers of birch veneer which have been dyed with aniline dye and then compressed under heat and pressure with acrylic resins into a dense, durable, highly polished material. Aniline dyes have been proven to be carcinogenic as well as sensitizing agents causing allergic contact dermatitis.
Aniline Dye (in Dymondwood)
Warning: this dye is also commonly used overseas to dye wood to make it appear as black ebony. Unfortunately, this practice is more common then you would believe.
Skin Contact: May be absorbed through skin. Symptoms of skin absorption parallel those from inhalation exposure. May cause skin irritation. Local contact may cause dermatitis.
Chronic Exposure: Aniline is a blood toxin, causing hemoglobin to convert to methemoglobin, resulting in cyanosis. Lengthy or repeated exposures may result in decreased appetite, anemia, weight loss, nervous system affects, and kidney, liver and bone marrow damage. Any exposure may cause an allergic skin reaction.
Skin Protection: Wear impervious protective clothing, including boots, gloves, lab coat, apron or coveralls, as appropriate, to prevent skin contact.
Environmental Toxicity: This material is expected to be very toxic to terrestrial life and to aquatic life.
It is possible that once sensitized to one of these quinones that cross reactions to similar quinones and/or structures
can develop. Included at the bottom of this page is a list of some of the more popular woods that are not suitable to
wear due to these risks. There are other hardwoods that are notorious for causing dangerous reactions (which may
include surprisingly strong reactions such as cardiac and nervous system effects, cancer, and genotoxicity), such as:
afromosia (Periocopsis elata), Australian blackwood (Acacia melanoxylon), greenheart (Chlorocardium rodiei),
mansonia (Mansonia altissima), sassafras (Sassafras albidum), and satinwood (Chloroxylon swietenia), as well as
various softwoods such as: cedar (Thuja spp.), hemlock (Tsuga spp.), pine (Pinus spp.), and yew (Taxus spp.);
however, these are not discussed here because we have fortunately not seen their attempted use in body jewelry.
Other compounds
Some of the other compounds that are known to cause harmful responses include: alkaloids and glycosides
(systemic effects, pharmacological rather than allergic), saponins (effective through broken skin only), phenols (the
strongest skin-sensitizers, especially the catechols of the poison-ivy family), stilbenes (which occur in allergenic
woods, but only chlorophorin and coniferyl benzoate are known to sensitize), terpenes (including delta-3-carene from
turpentine, sesquiterpene lactones and other sensitizing liverworts found on bark, and euphorbol and other complex
terpenes on uncertain toxicity found in the latex of Euphorbiaceae), coumarins and furocoumarins (photosensitizing
and may be partly responsible for skin reactions but has yet to be proven), and dalbergiones (severe skin irritants).
List of popular woods that should be avoided to minimize the risk of adverse effects
Most of this information is taken from: Botanical Dermatology: Plants and Plant Products Injurious to the Skin.
We will continue to expand this list as we further our research. Note that we are listing research specific to the
heartwood of trees; toxins can be found in a species that is not found in its wood. For example, cyanide is found in
apple seeds, but the fruit is edible, even though it is in close proximity to this toxin. “Toxic activity is specific to a
wood species. Knowing the exact species is important in establishing what the potential toxic effects may be.
Individual wood species… are very easily confused. For example, ‘rosewood’ may be used for up to 30 different
species; and an individual species may have up to ten different trade names (Hausen 1981). An additional difficulty
is that trees vary within a species. One specimen may contain low levels of its toxic agent and the next contain much
higher levels. So experience may not be a reliable guide.”
Dalbergia spp: (Rosewoods) “The discovery of sensitizing quinones in other woods such as teak…led Schulz and
Dietrichs (1962) to look for similar substances in Dalbergia nigra and Dalbergia retusa. They found three quinones
which they called Dalbergia quinones A, B and C, and demonstrated by patch tests on patients that these were the
sensitizers, the strongest being R-3,4-dimethoxydalbergione… They have now been found in most other Dalbergia
spp.”
Dalbergia cearensis: (Kingwood, de Violette, Violet Wood, Violetta) contains a dalbergione, described as a very
severe skin irritant, often leading to persistent ulceration.
Dalbergia cochinchinensis: (Laos Rosewood, Thai Rosewood, Cochin Rosewood) contain R-4-
methoxydalbergione and other quinones.
Dalbergia congestiflora: (Mexican Kingwood) contains a dalbergione.
Dalbergia cultrate: (Burmese Rosewood) contains a dalbergione.
Dalbergia decipularis and Dalbergia frutescens: (Tulipwood) contains a dalbergione.
Dalbergia latifolia: (East Indian Rosewood, Sonokoling) contain R-4-methoxydalbergione and other quinones.
Dalbergia maritime: (Madagascar Rosewood, Bois de Rose) contains a dalbergione.
Dalbergia melanoxylon: (African Blackwood) contains several quinones including S-4'-hydroxy-4-
methoxydalbergione and S-4-methoxydalbergione.
Dalbergia nigra: (Brazilian Rosewood) contains R-4-methoxydalbergione and other quinones.
Also endangered.
Dalbergia retusa: (Cocobolo) contains S-4'-hydroxy-4-methoxydalbergione, R-4-methoxydalbergione,
obtusaquinone, and other quinones and phenols.
Dalbergia stevensonii: (Honduran Rosewood, Nagaed Wood, Palissandre Honduras) contains a dalbergione.
Acer saccharum: (Sugar Maple) “This species has been found to contain 2,6-dimethoxy-1,4-benzoquinone which is a
known contact allergen.”
Betula spp: (Birch) contains salicylates such as methyl salicylate. Cross-sensitivities could occur in those with
aspirin allergies. Birch is also listed as sensitizer.
Cinnamomum camphora: (Camphorwood) The wood contains camphor and borneol. Following cases of serious
toxicity and even death in children, products conta ining more than trace quantities of camphor have now largely been
withdrawn from the market (Reynolds 1996). “Can cause dermatitis and shortness of breath” and camphor causes
mild heart stimulant activity. Topically applied, it can penetrate the skin.
Cordia dodecandra: (Zericote, Ziricote) Cross reactions are possible with this species once sensitivity to R-3,4-
dimethoxydalbergione (found in pao ferro and Dalbergia species), obtusaquinone (found in cocobolo), and macassar
quinone (found in macassar ebony) have developed.
Cordia elaeagnoides: (Bocote, Becote) Cross reactions are possible with this species once sensitivity to R-3,4-
dimethoxydalbergione (found in pao ferro and Dalbergia species), obtusaquinone (found in cocobolo), and macassar
quinone (found in macassar ebony) have developed.
Diospyros celebica: (Macassar Ebony) contains macassar II, a ß-naphthol “derivative that may become oxidised in
vivo to macassar quinone. This compound has been shown to have sensitizing properties in guinea pigs. Cross-
sensitivity to other naphthoquinones” (three found in zericote, pao ferro, cocobolo, becote, and padauk) are possible.
“Later testing confirmed sensitivity to R-3,4-dimethoxydalbergione (found in pao ferro), obtusaquinone (found in
cocobolo), and macassar quinone (found in macassar ebony).” Wood of this specie is one of the only ones that these
substances have been proven to occur in. “The yellow naphthoquinone pigment, plumbagin (methyl juglone) occurs
in a colourless combined form and is liberated from root tissue by acid treatment. (Harborne 1966)… Plumbagin is
also found in some species of the families Droseraceae, Ebenaceae, and Euphorbiaceae (Thomson 1971)….
Plumbagin has an irritating odor and causes sneezing; it stains the skin to a purple color and has a vesicant action.”
Guibourtia tessmannii: (Bubinga) “Dermatitis, possibly caused by sensitizing quinones.”
Machaerium scleroxylon: (Pau Ferro) has R-3,4-dimethoxydalbergione, a strong sensitizer and irritant. It can
cause dermatitis, itching, swelling, redness of face, scrotum, and hands.
Milletia laurentii: (Wenge) can have central nervous system effects, give dermatitis, irritate skin, is listed as a
sensitizer, and is oily.
Wenge contains 2.6-dimethoxybenzoquinone.
Peltogyne densiflora: (Purpleheart) “Dalbergiones have been isolated from the wood.”
Pterocarpus soyauxii: (Padauk) can cause irritation of the skin, dermatitis, and sensitization. It can have
naphthoquinones. Cross-sensitivity may occur with use of bocote when sensitivity has been developed to related
quinones.
Salix spp: (Willow) contains salicin, a phenolic glucoside, and is a precursor of aspirin; also has saligenin, a known
contact allergen. Willow is also listed as a sensitizer.
Tectona grandis: (Teak) The “dermatic compounds” (sensitizers) lapachol (aka tecomin, a quinone), desoxylapachol,
and lapachonole (aka lapachonone) where found in Tectona wood. Lapachol has been called “a known elicitor of
contact dermatitis” and a “sensitizing agent.” “Deoxylapachol and lapachenole…are potent contact allergens.” “Local
races of teak and even individual trees vary greatly in desoxylapachol content.” “Lapachenole has been shown to be
both irritant and sensitizing” by Sandermann & Barghoorn (1955). “Indonesian natives have long distinguished three
grades of the wood, the poorest (Djati sempoerna) being liable to cause skin irritation.”
Tetraclinis articulata: (Thuya Burl) The heartwood of this species is known to contain several dermatologically active
compounds including thymoquinone, carvacrol, and ß- and ã-thujaplicins.
Other wood related products
Dymondwood® is a manufactured plywood product consisting of laminated layers of hardwood (likely birch) veneer
which have been colored with mono-azo acid dyes and then compressed under intense heat and pressure with
phenol formaldehyde resin into a dense, durable, highly polished material. Interestingly, Bakelite, a type of early
thermoset synthetic resin, is a polymer of phenol with formaldehyde. Many Dymondwood® varieties go by cute trade
names, but it can usually be identified by it's appearance as a brightly colored wood product with consistently spaced
stripes in contrasting colors not normally appearing in untreated wood. Besides cropping up periodically in the body
piercing world as earplugs, it is common to find it utilized in other products such as pipes and bracelets.
Phenol, also known as carbolic acid or hydroxybenzene, is toxic and corrosive. The dangers posed by formaldehyde,
including it’s role as a carcinogen, are also substantial. According to the MSDS for Dymondwood®, "Phenol and
formaldehyde may be released in small quantities from product under normal conditions." “Some people may
develop dermatitis from repeated and prolonged exposure to unfinished product.” “Laboratory data indicates that
certain acid dyes may be mutagenic in animals.”
The azo dyes (azo is a chemical compound containing one pair
nitrogen atoms with a double bond between them) may release aromatic amines if the azo linkages are broken down
via enzymes, or poss ibly via heat and photochemical reactions, though intact azo dyes are unlikely to be absorbed by
the skin. However, these aromatic amines have been linked to serious long-term health effects, including links to
cancer in humans, so the possibility of their presence is of grave concern. Incidently, azo dyes are sometimes used
as pigments in tattoo ink.
Unfortunately, dyes are also commonly used overseas to make lighter woods appear as black ebony. These
commonly include aniline or PPD. Aniline is a blood toxin that is easily absorbed through the skin, which may cause
allergic skin reactions and irritation, contact dermatitis, sensitization, is a possible carcinogen, and is considered very
toxic to terrestrial and aquatic life.
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