Recognizing the Toxicodendrons (poison ivy, poison oak, and poison sumac)

Poison ivy, poison oak, and poison sumac are now classified in the genus Toxicodendron which is readily distinguished from Rhus. In the United States, there are two species of poison oak, Toxicodendron diversilobum (western poison oak) and Toxicodendron toxicarium (eastern poison oak). There are also two species of poison ivy, Toxicodendron rydbergii, a nonclimbing subshrub, and Toxicodendron radicans, which may be either a shrub or a climbing vine. There are nine subspecies of T. radicans, six of which are found in the United States. One species of poison sumac, Toxicodendron vernix, occurs in the United States. Distinguishing features of these plants and characteristics that separate Toxicodendron from Rhus are outlined in the text and illustrated in color plates.     

A study of cross-reactions between mango contact allergens and urushiol

The allergens causing mango dermatitis have long been suspected to be alk(en)yl catechols and/or alk(en)yl resorcinols on the basis of observed cross-sensitivity reactions to mango in patients known to be sensitive to poison ivy and oak (Toxicodendron spp.). Earlier, we reported the 3 resorcinol derivatives: heptadecadienylresorcinol (I), heptadecenylresorcinol (II) and pentadecylresorcinol (III); collectively named 'mangol', as mango allergens. In this study, we extracted the 1st 2 components (I and II) from the Philippine mango, adjusted them to 0.05% concentration in petrolatum and patch tested the components on 2 subjects with mango dermatitis. Both subjects reacted to I. 1 subject also elicited a weaker positive reaction to II. To investigate the cross-reaction between mangol and urushiol, we also patch tested the same subjects with urushiol. The subject sensitive to II reacted to urushiol. 6 subjects with a history of lacquer contact dermatitis and positive reactions to urushiol were similarly patch tested. 5 persons reacted to I. 2 subjects also exhibited a slower but positive reaction to II. This is the 1st report in which heptadec(adi)enyl resorcinols known to be present in mango have been shown to elicit positive patch test reactions in mango-sensitive patients.     

Induction of tolerance to poison ivy urushiol in the guinea pig by epicutaneous application of the structural analog 5-methyl-3-n-pentadecylcatechol

Previous studies have established that epicutaneous application of 5-methyl-3-n-pentadecylcatechol (5-Me-PDC), a synthetic analog of a poison ivy urushiol component, leads to immune tolerance to 3-n-pentadecylcatechol (PDC) in mice. The induction of tolerance by 5-Me-PDC may be mediated by a protein conjugate formed via selective reaction of thiol nucleophiles present on the carrier macromolecule with the corresponding o-quinone derived from the parent catechol. In order to examine further the tolerogenic properties of 5-Me-PDC, we have extended our studies to the guinea pig, the generally accepted experimental species for the study of contact allergy. The results have established that specific immune tolerance to poison ivy urushiol is induced following 2 epicutaneous applications of the PDC analog. Furthermore, we were able to show that the treated animals remained tolerant for at least 6 weeks, a period of time comparable to that observed following the intravenous administration of the O,O-bis-acetyl derivative of PDC. The data point to the possibility of developing a therapeutically effective topical tolerogen for poison ivy contact dermatitis.     

Regulation of the contact sensitivity response to urushiol with anti-urushiol monoclonal antibody ALG 991

The objective of the studies was to demonstrate that the contact sensitivity (CS) response to poison ivy/oak could be downregulated following treatment with a monoclonal antibody (mAb) reacting with the allergen urushiol. Conjugation of urushiol and its synthetic analogue 3-n-pentadecylcatechol (PDC) to N-acetylcysteine yielded hydrosoluble derivatives which induced humoral immune responses in BALB/c mice. Hybridomas secreting monoclonal antibodies (mAbs) reacting with urushiol and PDC were generated by fusion of B lymphocytes from immunized mice with mouse myeloma P3NS0 cells. The specificity of mAb ALG 991 (IgM isotype) was defined by inhibition of antibody binding by PDC analogues. This demonstrated that mAb ALG 991 reacted with the catechol moiety of urushiol, the region of the allergen being critically important in the induction of contact dermatitis. The CS response to urushiol in BALB/c mice was suppressed by stimulation with mAb ALG 991 and the role of sensitized T cells, including suppressor T cells, has been considered. Suppression of CS was most effective with low doses (1 microg) of mAb incorporated into a vaccine with Freund's adjuvant. This treatment suppressed CS responses in BALB/c mice already sensitized to urushiol.     

Hyposensitization to poison ivy after working in a cashew nut shell oil processing factory

19 adults were patch tested to urushiol, the allergen in poison ivy/oak, to determine their sensitivity to this allergen after working in a cashew nut shell oil (CNSO) processing plant. The cashew nut tree and poison ivy/oak are in the same botanical family. Anacardiaceae, and they share similar chemicals which cause allergic contact dermatitis. 13 of the 19 workers had a preemployment history of poison ivy sensitivity, with 10 developing CNSO dermatitis. After working in this factory for several months, 9 of the 13 noticed a decreased sensitivity or no sensitivity to poison ivy/oak. When tested to urushiol extract, only 3 reacted positively, 2 minimally. These results imply that hyposensitization to poison ivy/oak occurred in these employees after development of hardening to cashew nut shell oil.     

Regulation of murine contact sensitivity to urushiol components by serum factors

Mice epicutaneously painted with components of poison ivy urushiol oil exhibit contact sensitivity (as detected by ear swelling reactions) that persist for about 25 days. Sera taken from mice at times when the contact sensitization response is waning suppressed the induction of sensitization to 3-n-pentadecylcatechol (PDC), a urushiol component, in recipients. The suppressive serum factor was present in greatest amount 25 days after sensitization, but was no longer detectable 40 days post sensitization. Suppression was antigen-specific, absorbed out with PDC-immune, but not normal lymph node cells, and transferable with a single 0.6 ml dose 7 days prior to sensitization of recipients. Suppression was transferable by the purified IgG fraction of desensitized mice. Results indicate that contact sensitivity to urushiol in mice is regulated by serum factors.     

Assessment of the ability of the topical skin protectant (TSP) to protect against contact dermatitis to urushiol (Rhus) antigen.

BACKGROUND: Military personnel have a need for effective protection against cutaneous exposure to chemical warfare agents (CWA). Topical Skin Protectant (TSP) is being developed to supplement chemical warfare protective garments. TSP protects against CWA exposure in animals, but does it work for humans? Because humans should not be tested with live CWA, urushiol (poison ivy) extract was used as a surrogate substance in place of CWA for human efficacy testing of TSP. OBJECTIVE: Determine whether TSP protects human skin against experimentally-induced urushiol dermatitis. METHODS: Open urushiol patch testing of 50 rhus-sensitive subjects comparing the 96-hour dermatitis severity scores between TSP protected and TSP unprotected sites. There were 4 paired sites (i.e., protected versus unprotected) per subject. Test sites were scored using a 9-point dermatitis scale of 0.0 to 4.0 (using 0.5 increments). RESULTS: Analysis of variance of the dermatitis scores from 192 paired sites on 48 evaluable subjects showed that TSP protected sites had mean dermatitis scores about 2 points lower than TSP unprotected sites (P <.001). CONCLUSION: Although this study does not provide direct scientific evidence that TSP protects humans against the percutaneous absorption of CWA, it does provide circumstantial evidence that this is the case. The fact that TSP is so highly effective against a lipophilic substance like urushiol and that most common vesicant CWAs are lipophilic and are weaponized in oleaginous vehicles, makes the effectiveness of TSP in preventing absorption and dermatitis from CWA seem likely.     

Toxicodendron radicans dermatitis with black lacquer deposit on the skin

Four patients with clinical Toxicodendron dermatitis (poison ivy) presented with dramatic black lacquer-like deposits on several lesions. This black deposit was also observed at sites of injury on poison ivy plants and was reproduced on volunteers by the application of plant sap on the skin. Histologically, the observed material was identified in the stratum corneum. This little-recognized phenomenon has been mentioned in past dermatologic literature.     

Recent developments in the pathogenesis of allergic contact dermatitis

Allergic contact dermatitis is both an important clinical problem and a model system for lymphocyte-mediated pathologic changes. Elicitation of allergic contact dermatitis requires interaction of antigen with epidermal Langerhans cells, followed by migration of the Langerhans cells to the lymph nodes to present antigen to T lymphocytes. These activated T lymphocytes must then home to the antigen-exposed skin. Adhesion molecules such as LFA-1 and ICAM-1 have a role in this homing. Only a small proportion of the T lymphocytes in the skin lesion are specific for the inducing antigen. Studies of poison ivy (urushiol dermatitis) have determined this fraction to be less than one per 100 infiltrating lymphocytes. By a variety of amplification mechanisms, it is possible for this small number of antigen-specific T lymphocytes to induce the pathologic changes of allergic contact dermatitis. Improved understanding of this condition should result in increased knowledge of the pathogenesis of a variety of T lymphocyte-mediated skin conditions.     

Black spot poison ivy: A report of 5 cases and a review of the literature.

Black-spot poison ivy dermatitis is a rare manifestation of a common condition. It occurs on exposure to the resins of the plants of the Rhus family also known as Toxicodendron. We describe 5 patients with black deposits on their skin and clothing after contact with poison ivy and review the literature reflecting different aspects of this phenomenon including clinical presentation, histologic findings, and historical background.     

Smodingium allergenic Anacardiaceae in South Africa

The first case reports of genuine poison ivy dermatitis in South Africa appeared in 1959.¹ Eight patients were seen who had developed the rash following contact with a creeper in a hedge in Olifantsfontein near Pretoria. The creeper was identified as Toxicodendron radicans and had presumably been imported from North America, since it is not indigenous to South Africa. Similar cases have been seen since then in Johannesburg.²In 1963, seven patients from Pretoria and Johannesburg with a unique dermatitis of “poison-ivy type” were reported.³ These patients had not been exposed to imported American poison ivy but had reacted to an indigenous plant identified as Smodingium argutum, known by various common names, including tovana and rainbow leaf. It transpired that Smodingium dermatitis had been recognized by tribal blacks, foresters, botanists, horticulturists, and amateur gardeners for many years before the medical profession became aware of it. In subsequent years, this type of dermatitis became widely recognized and many more cases were seen, leading to further case studies² and investigations.^4,5In 1971. four South African patients were reported with a similar type of “poison ivy” dermatitis who had been exposed to the wax tree, Toxicodendron succedanea, an oriental sumac.² It became clear from cross-sensitivity reactions in certain patients that there were antigenic similarities between the oleoresins from S. argutum, T. radicans and T. succedanea, all members of the family Anacardiaceae.² An identical dermatitis is produced by all three plants.     

Topical prevention of poison ivy/oak dermatitis

An organoclay preparation was evaluated for topical protection against experimental poison ivy/oak in a rigorous double-blind study. By direct comparison with the same subject, it proved more effective than comparable preparations of bentonite, kaolin, or silicone in 16 of 17 trials. When evaluated globally against control responses to urushiol the organoclay preparation gave 95.3% protection against topical urushiol applications, ranging from 4.75 to 0.0475 nmol. Bentonite, kaolin, and silicone gave 29.6%, 37.9%, and 32.9% protection, respectively, in the same system. We conclude that organoclay is an effective topical protectant against experimental poison ivy/oak dermatitis, and deserves further clinical evaluation.     

FS11.5Toxicodendron dermatitis in the United Kingdom

We describe two cases of Toxicodendron dermatitis, one acquired in the United States but presenting in the United Kingdom, the other a recurrent dermatitis following importation to the UK. Poison ivy, poison oak and poison sumac are native to North America and belong to the genus Toxicodendron. This group of plants is of interest to the dermatologist because they contain a mixture of potent sensitisers which cause a severe allergic contact dermatitis. The dermatitis can present to the dermatologist in Europe after an individual has been in contact with the plant whilst visiting an endemic area. The plants have the potential to grow in the UK and it is therefore possible for an individual to be sensitised and subsequently to develop the rash without leaving the UK. A 35‐year‐old American man who lived in the UK visited his family in Marietta, Georgia USA. Shortly before his return to the UK he cut some plants back in his mother’s garden. Two days following his arrival back in the UK he developed a widespread pruritic and painful vesicobullous eruption. He required admission for intensive potent topical corticosteroid therapy and the eruption settled over the next two weeks. The plant he had been pruning was subsequently identified as poison sumac (Toxicodendron vernix). A 54‐year‐old woman living in Wales was referred to the Contact Dermatitis Investigation Unit because during the summer months for the previous four years she had experienced an intermittent, intensely pruritic, vesicular and in parts linear eruption affecting her face, arms and legs. This responded slowly to potent topical corticosteroids. She is a keen gardener and suspected that it was related to a plant in her garden. She was patch tested to our Standard Series, Plant Series and all the plants in her garden. She showed ++ allergic reactions to sodium metabisulphite, propolis and a strong vesicular reaction to the leaf of one of the plants from her garden Inspection of the plant revealed that it had three leaflets per stem. She had taken a cutting whilst visiting friends in Pennsylvania in 1996 and on returning to the UK had planted it in her garden. It grew but had never flowered or produced seeds. Once the cause of her dermatitis had been confirmed our patient took the necessary protective measures and removed the plant including its roots from her garden. She has not experienced any further problems with her skin. She contacted her friends in the USA who knew precisely where she had picked the plant. A further specimen was taken to the local Conservation Office where it was confirmed to be poisonivy. Poison ivy and poison sumac belong to the genus Toxicodendron which is native to North America and Mexico. They cause an allergic contact dermatitis when there is exposure to a bruised portion of the plant. This leads to the oleoresin, urushiol coming into contact with the skin. 25–60% of North Americans are reported be allergic to poison ivy and its relatives. The importation of plants into the UK is restricted by law. It is clear that this plant grew in its new habitat but did not extend beyond the confines of the garden. With frequent and more extensive air travel it seems reasonable to speculate that similar occurrences have taken place and that plants not endemic to Europe should be considered in those with suspected plant dermatitis.     

Toxicodendron dermatitis in the UK

BACKGROUND: We present two cases of Toxicodendron dermatitis, one acquired in the United States but presenting in the United Kingdom (UK), the other a recurrent dermatitis following importation of the plant to the UK. Poison ivy, poison oak and poison sumac are native to North America and belong to the genus Toxicodendron. This group of plants is of interest to the dermatologist because they contain a mixture of potent sensitisers which cause a severe allergic contact dermatitis. CONCLUSIONS: The dermatitis can present to the dermatologist in Europe after an individual has been in contact with the plant whilst visiting an endemic area. The plants have the potential to grow in Europe and it is therefore possible for an individual to be sensitised and subsequently to develop the rash without leaving the continent.     

Treatment of toxicodendron dermatitis (poison ivy and poison oak)

Toxicodendron dermatitis results from a reaction to an oil soluble oleoresin that is present in many parts of the poison ivy and poison oak plants. Prophylactic measures include avoidance, protective clothing, barrier creams and hyposensitization. Treatments include washing the area immediately with a solvent suitable for lipids and the use of anti-inflammatory agents, especially corticosteroids.     

Polymerized Urushiol of the Commercially Available Rhus Product in Korea

Background

Systemic contact dermatitis commonly occurs with the intake of rhus (boiled chicken with rhus) as a health food and a folk medicine to cure gastrointestinal diseases in Korea. Rhus companies insist they have the technology for rhus detoxification. However, the numbers of systemic allergic contact dermatitis patients, caused by rhus, have not decreased. The principle of present techniques for rhus detoxification is the induction of the polymerization of urushiol, but polymerized urushiol may still have antigenicity, although to a diminished degree. The Korean Food and Drug Administration (KFDA) has a regulation to control urushiol use as a food. However, the laboratory method that KFDA uses for detection of rhus can only detect the urushiol monomer.

Objective

We conducted experiments to detect polymerized urushiol in rhus products, which were considered not to include urushiol by the KFDA.

Methods

Rhus product approved by the KFDA was separated with chloroform. The chloroform fractionation was accomplished on a recycle HPLC system. Four peaks were achieved and evaporated to give an amorphous powder. Each powder was analyzed on a NMR system and mass spectrometer.

Results

The material considered to be urushiol dimer, with a 638 molecular weight (MW), was detected in one of the four powders as per the HPLC peaks.

Conclusion

We concluded that commercially available rhus product is comprised of material considered to be urushiol dimer. Therefore, even if the antigenicity of the rhus products is low, this product may cause adverse effects and is not completely detoxified.     

A potent contact allergen of Phacelia (Hydrophyllaceae)

The major contact allergen of Phacelia crenulata (Hydrophyllaceae) has been identified as geranylhydroquinone. A maximization test of geranylhydroquinone showed this to be a potent sensitizer comparable in degree to poison oak/ivy urushiol. Comparative patch testing on humans with urushiol established that the Phacelia allergen does not cross-react with poison oak or ivy.     

T-lymphocyte cytokine profiles in compositae airborne dermatitis

Compositae airborne dermatitis is a well-recognized disorder characterized by erythematosquamous lesions and papules on light-exposed areas. The presence of positive patch test reactions and the absence of specific serum IgE suggest delayed-type hypersensitivity, the murine model of which is characterized by a Th1 cytokine production profile [high amounts of interferon (IFN)-gamma and interleukin (IL)-2; little or no IL-4 and IL-5]. The aim of this study was to evaluate the cytokine profile of T-cell lines and T-cell clones from peripheral blood in a 38-year-old non-atopic male woodcutter affected by seasonal airborne contact dermatitis. The patient showed positive patch test reactions to several Compositae extracts (Achillea millefolium, Chamomilla recutita, Tanacetum parthenium, T. vulgare) and sesquiterpene lactone mix. On prick testing with Compositae and other plants, serum-specific IgE levels and phototesting were negative or normal. Allergen-specific T-cell lines produced with Compositae extracts showed a good in vitro cell proliferation only to C. recutita extract. Serial cloning performed using the C. recutita-specific T-cell lines revealed an alphabeta+CD4+ phenotype with high amounts of IFN-gamma and IL-4 in T-cell clones. Thus, these cells expressed a preferential Th0 phenotype. These data suggest that in addition to IFN-gamma, other T-cell derived cytokines, such as IL-4, may play a part in the immunopathogenesis of contact dermatitis.     

Suppression of urushiol-induced delayed-type hypersensitivity responses in mice with serum IgG immunoglobulin from human hyposensitized donors

Serum IgG immunoglobulin fractions from human subjects hyposensitized to poison ivy/oak by oral administration of urushiol suppressed the induction of delayed-type hypersensitivity (DTH) responses in mice to this hapten. This suppressive activity was hapten specific because it did not modify DTH responses to dinitrofluorobenzene (DNFB). Absorption of human serum with lymph node cells from urushiolsensitized but not DNFB-sensitized mice removed the suppressive activity, suggesting that anti-idiotypic antibodies reacting with T-cell receptors are involved.     

Kontaktallergie auf Poison ivy (Toxicodendron spp.)

Within 3 days two female patients presented with an eruption featuring erythema, edema, vesicles and bullae. We suspected poison ivy allergy which was subsequently proven by history and positive patch tests. In Germany the risk of specific hypersensitivity to Toxicodendron species is low, since the distribution of such plants is confined to botanical gardens. Other species belonging to the family of Anacardiaceae contain urushiols as well (e.g., mango, cashew) and may cause allergic contact dermatitis.