Leaves of Three, How Bad Can It Be?

S C I E N C E O F M E D I C I N E

CAITLIN A. COCHRAN, BS; DANIELLE KEYES, MPH; CAROLINE DOO, MD; THY HUYNH, MD; JULIE WYATT, MD

Abstract

Poison ivy is a common cause of allergic contact dermatitis. A rare phenomenon, black spot poison ivy, presents with poison ivy covered by black lacquer-like deposits. Another equally rare phenomenon is the development of erythema multiforme in association with severe poison ivy. 1-4 The treatment of mild poison ivy contact dermatitis usually requires only topical therapies, but more severe cases require systemic approaches. 1,5 A 36-year-old male with black spot poison ivy treated with topical, intramuscular, and oral steroids who subsequently developed secondary erythema multiforme is presented.

Key Words: Allergic contact dermatitis; Toxicodendron species; Black spot poison ivy; Erythema multiforme

Introduction

A 36-year-old male presented with a two-week history of rash on the left forearm and a secondary rash on the abdomen following contact with a vine which he documented with a series of four “selfies.” (Figure 1 and 2)

Patient’s left volar forearm on day 1 depicting erythematous plaque with ulceration and black spots.

Patient’s left volar forearm on day 3 depicting erythematous plaque with ulceration and black spots with vesicles and crust.

The rash was associated with severe pruritus, erythema, and exudate. A five-day tapering course of oral prednisone and an IM injection of 1 cc of triamcinolone 40mg/cc along with topical betamethasone 0.05% cream led to modest improvement and then a flare. (Figure 3 and 4) His past medical history was significant for celiac disease and chronic sinusitis. Dermatologic examination revealed large edematous red plaques with erosions on bilateral ventral forearms with greater involvement of the right arm. Scattered symmetric erythematous, edematous, targetoid plaques were present on the abdomen. (Figure 5)

A diagnosis of black spot poison ivy with secondary erythema multiforme was made. Treatment was initiated with cyclosporine 4 mg/ kg by mouth daily for one week and tapered over the subsequent two weeks. The patient experienced a mild headache, which resolved with ibuprofen, after the first dose of cyclosporine. The pruritus resolved within 24 hours. The rash from allergic dermatitis steadily improved and completely resolved by day 20 after cyclosporine was initiated. Mild targetoid lesions associated with erythema multiforme continued to occur even six weeks after cyclosporine was completed. No antibiotics were used during the treatment course.

Patient’s left volar forearm on day 4 depicting violaceous erythema with a linear bulla and a central black linear patch.

Discussion

The Anacardiaceae family of plants is widely distributed across the United States. (Table 1) Toxicodendron radicans and Toxicodendron rydbergii are the two poison ivy species that are colloquially known as Eastern (or common) poison ivy and Western (or Northern) poison ivy, respectively. The two poison oak species are Toxicodendron toxicarium (Eastern poison oak) and Toxicodendron diversilobum (Western poison oak). There is one species of poison sumac, Toxicodendron vernix. 7

Identification of the plants that can cause an allergic contact dermatitis is critically important for preventing the development of allergic contact dermatitis or recurrence of the condition. 1 Toxicodendron plants have compound leaves, meaning they have at least three leaflets that compose each leaf. This feature is what led to the old adage, “Leaves of three; leave them be.” 7 All the Toxicodendron species possess green fruit clusters found in the angle between the leaf and twig from where it grows. The clusters of fruit will turn off-white as they mature in the fall.

Additionally, Toxicodendron species will leave a “U” or “V”-shaped scar when a leaf stalk falls from the plant. 1,7 The species can be further identified based on number of leaflets and growth patterns. Toxicodendron radicans typically has oval leaflets found in groups of three with the longest and biggest leaflet found in the center. This species is commonly found along streams, trails, or roads, and usually has aerial rootlets that allow it to climb like a vine. Toxicodendron rydbergii is similar to Toxicodendron radicans but typically has thicker stems and more commonly grows like a shrub because it does not have aerial rootlets as frequently. Toxicodendron toxicarium has three to five oval leaflets per leaf and grows in sandy soils or disturbed ground in a shrub-like manner. Toxicodendron diversilobum also has three to five oval leaflets per leaf but has aerial roots allowing it to grow as a vine in canyons, riparian habitats, and on tree trunks. Finally, Toxicodendron vernix is found mostly in swampy areas as bushes with leaves composed of seven to 13 leaflets organized in pairs with a central rib and one leaflet at the end. 1 (Table 1)

Patient’s left volar forearm on day 4 depicting black spot with ulceration and crust with lymphangitis.

Patient’s abdomen on day 19 with targetoid violaceous edematous plaques.

Table 1. Geographic distribution of the most common species in the Toxicodendron genus that cause allergic contact dermatitis in the United States. Plant images represent the species that can be found in Mississippi.

Source: USDA, NRCS. 2018. The PLANTS Database (http://plants.usda.gov, 22 May 2018). National Plant Data Team, Greensboro, NC 27401-4901 USA. 10-12

Urushiol, also known as oleoresin, is a chemical compound that is found in the sap of plants in the Anacardiaceae family. The chemical compounds found in the different species are very similar; they are 1,2-dihydroxybenzenes with a 15-carbon-atom side chain in the third position. 13,14 The resin canals in the plant do not communicate with the leaf surface under normal conditions, and therefore, physical contact with the plants will only cause a hypersensitivity reaction if the plant surface has been damaged. 1,15 However, it is important to note that the plants will release urushiol in the absence of damage during late fall. 7 The sap of the plant is also found in the stem or other plant parts that can be present even in the absence of leaves like in the winter. 1,9 Prevention is best accomplished by avoiding allergen exposure altogether. The use of skin protectants (zinc acetate, zinc carbonate, and zinc oxide) prior to exposure and rinsing of the exposed area within 30 minutes after contact can minimize the allergic reaction. If rinsing begins at ten minutes after exposure, fifty percent of the oil can be removed; however, at thirty minutes after exposure, only ten percent of the oil is removed. Patients should be advised to rinse affected areas gently as soon as possible after exposure. 1,7

Urushiol is typically colorless or light yellow but turns black when it is exposed to air due to polymerization and subsequent oxidation. 1 Once the sap is present on the skin, clothing, or under the nails, it can persist for weeks and even months. The urushiol present on the skin acts as a hapten, which is absorbed through the skin and taken up by Langerhans cells and macrophages in the epidermis and dermis, respectively. These cells then travel to the lymph nodes and activate CD4 T lymphocytes which subsequently produce clones of effector and memory T cells specific for the urushiol antigen. After the first exposure to the antigen, the clonal T lymphocytes will cause symptoms within 24 to 48 hours of exposure. 1

Patients with poison ivy contact dermatitis will characteristically present with a generalized, pruritic, erythematous rash with vesicles and papules in a linear distribution. In rare cases, patients will present with black lacquer-like macules with surrounding edema, background erythema, and vesicles. This special variant of poison ivy will occur if the patient is exposed to a high concentration of the urushiol that is not diluted. 15,

This concentrated urushiol is oxidized on exposure to air, turning black within the first 24 hours after exposure. Interestingly, this has been used as a method of identifying poison ivy in the field. When the leaves are placed on white paper, crushed, and then discarded, there will be a resulting black stain within a few minutes of exposure to the air. 17 The concentrated resin or urushiol in black spot poison ivy can deposit on almost any surface, including the skin and clothing. It can present asymptomatically in some cases where they appear to be black lesions that the person cannot wash off. The same resin can deposit in clothing which, even after washing or boiling, can indefinitely cause allergic contact dermatitis. 7,9

Histologic findings of allergic contact dermatitis due to poison ivy include perivascular lymphohistiocytic infiltration and subepidermal blisters with eosinophils and eosinophilic spongiosis. The black spot variant specifically demonstrates yellow amorphous material representing the urushiol in the stratum corneum along with epidermal necrosis with nucleolar fragments and neutrophils. 9,15

Mild Toxicodendron allergic contact dermatitis is managed with symptomatic treatments such as lukewarm baths, calamine lotion, and oral antihistamines. The goal of topical therapy is to control the pruritus. High potency topical corticosteroids do not alter the disease progression of contact dermatitis after vesicles have formed, but they have been shown to improve pruritic symptoms of patients.18 When more than 25% body surface area is affected, when blistering or pruritus are severe, or when there is significant involvement of the hands, face, or genitalia, systemic treatment is indicated. 5 The most common systemic treatment for adults is oral prednisone up to 1–2 mg/kg/day for a period of seven to 10 days, tapered over two weeks. It is important not to prescribe a pre-packaged course of oral glucocorticoids, such as a methylprednisolone dose pack, as the dosage is too low and the taper is too short to provide adequate treatment and increases the likelihood of a relapse. 1,5 Alternatively, we recommend cyclosporine at 4 mg/kg/day tapered weekly over three weeks can be used as a first line of treatment especially if the patient has relative contraindications to steroids such as diabetes.

Erythema multiforme is a hypersensitivity reaction associated with certain infections such as Herpes simplex virus and medication exposures. It has been reported after the development of severe poison ivy allergic contact dermatitis that required systemic treatment. Some authors speculate that while rare, it is also underreported. 2,3 There is little correlation between the timing of systemic steroid treatment and the onset of the rash. Therefore, it is unlikely that this is a reaction to the systemic steroids. 2-4 Other less common causes of contact dermatitis that have been associated with erythema multiforme and erythema multiforme-like reactions include nickel, essential oils, laurel oil, and topical triamcinolone. 3,19-21 Cyclosporine is a favored treatment for intermittent or severe erythema multiforme due to its rapid onset of action and mechanism of action which targets explicitly activated helper CD4+ T lymphocytes and prevents their production of IL2. 22

In summary, reactions from poison ivy can range from mild to severe. This form of contact dermatitis can cover large portions of the body including sensitive areas like the face and genitals. It is typically associated with severe itching that can lead to scratching and secondary infection. Rare presentations include black spot poison ivy and secondary erythema multiforme in association with severe poison ivy. Prevention of the initial rash can be achieved by avoiding the plant, using skin protectants, , and washing immediately following exposure. Appropriate treatment with topical and systemic agents can help minimize any secondary complications. �

Mythbusters

• Plants with “leaves of three” are not the only types of plants that can cause an allergic contact dermatitis. Poison sumac with seven to 13 leaflets contains the same Rhus antigen. 1

• Vesicular fluid does not contain antigen and, therefore, is not responsible for spreading the rash. 1

• A pre-packaged course of oral methylprednisolone, such as a methylprednisolone dose pack, is not an adequate treatment for poison ivy allergic contact dermatitis and can lead to a rebound effect. 5

Acknowledgment

We would like to acknowledge Dr. Stephen E. Helms for his contribution to the title of this publication.

References

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Author Information

M4, Louisiana State University Health Sciences Center, Shreveport (Cochran). University of South Alabama College of Medicine, Mobile (Keyes). PGY-2, Department of Dermatology, University of Mississippi Medical Center, Jackson. (Doo)(Huynh). Associate Professor in Dermatology, University of Mississippi Medical Center, Jackson (Wyatt).

Corresponding Author: Julie Wyatt, MD; UMMC Department of Dermatology, 2500 N. State St.,Jackson, MS 39216.