VisualDx - Diagnosis Details - Adult Rash: Dermatitis, Poison Ivy - Oak

692.6 – Contact dermatitis and other eczema due to plants [except food]

Poison ivy, poison oak, or poison sumac dermatides are type IV delayed hypersensitivity immune reactions to an oily resin (urushiol) found on the leaves and in the stems and roots of plants of the Rhus genus (poison ivy, oak, and sumac). It occurs in previously sensitized individuals. Skin lesions usually begin to appear 48 hours after initial exposure, and they usually consist of erythematous, linear plaques and vesicles on the extremities. Pruritus is often severe. If not washed away, the resin may be easily and unwittingly transferred to other body locations, where it will incite the same reaction. Poison ivy, oak, or sumac dermatitis can occur in people of all races and ages, although dark-skinned individuals, the elderly, and very young children may be less susceptible. Scratching does not spread lesions; the lesions with the most antigen appear first and then, as the immune response increases, lesions with less antigen begin to erupt. Symptoms are usually related to severe pruritus.

Look For

Linear, erythematous plaques and vesicles, most often on the extremities. Crusted plaques and bullae may be seen. A "black dot variant" has been described (where the oil from the plant leaves a black dot on the skin).

Diagnostic Pearls

A linear configuration of lesions on exposed extremities suggests the diagnosis. Take a careful history looking for potential exposures.

Other diseases with an external environmental exposure may mimic this disorder (ie, disorders with a light-related causation such as photoallergic reactions).

Differential Diagnosis & Pitfalls

Consider other causes of allergic contact dermatitis, including other plants. Mangos contain an antigen that cross-reacts with poison ivy oil and may result in perioral contact dermatitis.
Hogweed dermatitis
Arthropod bites or stings
Atopic dermatitis
Scabies can also have linear lesions, vesiculation, and be extremely pruritic.
Cellulitis or erysipelas
Herpes simplex infection
Bullous drug eruption
Nummular dermatitis
Tinea corporis or manus
Stasis dermatitis
Bullous impetigo
Zoster
Solar urticaria
Drug-induced phototoxic reaction
Phytophotodermatitis from exposure to limes or other psoralen-containing plants.
Bullous pemphigoid and herpes gestationis both demonstrate vesicles and bullae on the extremities.
Porphyria cutanea tarda

Best Tests

This is a clinical diagnosis.

Biopsy is rarely needed and will reveal a pattern consistent with dermatitis, not specific for poison ivy.

If necessary, patch testing can be conducted to rule out other causes of contact dermatitis.

Management Pearls

Patients should use a strong soap and water to wash all potentially exposed areas since the oil adheres avidly to the skin. Once the oil has been washed off, there is no risk of spreading the condition to other parts of the body. Be sure to wash garments as well.

Do not prescribe a 6-day course of quickly tapering steroids, such as Medrol® Dosepak™ as the delayed hypersensitivity reaction is at least a 2-week process. Shorter courses of oral steroids will result in a rebound flaring of the dermatitis.

Prevention is important. Advise patient to wear protective clothing and barrier cream (IvyBlock®, apply 15 minutes before potential exposure) to avoid future reactions. It is helpful if patients are able to recognize the offending plants.

Therapy

In severe cases involving large body areas, use a 14-day course of oral prednisone 0.5 mg/kg each morning and taper only slightly during the interval.

High-potency topical corticosteroids may be used on truncal and extremity skin when there is limited skin disease.

High-potency topical corticosteroids (class 2):

Fluocinonide cream, ointment (Lidex®) – apply twice daily (15, 30, 60, 120 gm)
Desoximetasone cream, ointment (Topicort®) – apply twice daily (15, 60, 120 gm)
Halcinonide cream, ointment (Halog®) – apply twice daily (15, 60, 240 gm)
Amcinonide ointment (Cyclocort®) – apply twice daily (15, 30, 60 gm)

Mid-potency topical corticosteroids (class 3–4):

Triamcinolone cream, ointment (Kenalog®, Aristocort®) – apply twice daily (15, 30, 60, 120, 240 gm)
Mometasone cream, ointment (Elocon®) – apply twice daily (15, 45 gm)
Fluocinolone cream, ointment (Synalar®) – apply twice daily (15, 30, 60 gm)

Use mild-potency topical steroids on thinner skin and class 6–7 steroids on the face (desonide cream, lotion, or ointment twice daily).

Topical calcineurin inhibitors (pimecrolimus 1% cream, tacrolimus 0.1% ointment) applied twice daily may be an alternative to topical corticosteroids in the treatment of the inflammatory response, if the patient tolerates them.

Antihistamines should be prescribed for the control of pruritus:

Diphenhydramine hydrochloride (Benadryl®) (25, 50 mg tablets or capsules): 25–50 mg nightly or every 6 hours, as needed
Hydroxyzine (Atarax®) (10, 25 mg tablets): 12.5–25 mg every 6 hours, as needed
Cetirizine hydrochloride (ZYRTEC®) (5,10 mg tablets): 5–10 mg per day

Additional comfort measures include cool tap water or Burow's solution compresses, colloidal oatmeal baths (Aveeno®), and calamine lotion.

Treat any secondarily infected lesions with the appropriate topical or systemic antibiotic.

References

Gladman AC. Toxicodendron dermatitis: poison ivy, oak, and sumac. Wilderness Environ Med. 2006;17(2):120-8. PubMed Id: 16805148

Goodall J. Oral corticosteroids for poison ivy dermatitis. CMAJ. 2002 Feb 5;166(3):300-1. PubMed Id: 11868634

Guin JD. Treatment of toxicodendron dermatitis (poison ivy and poison oak). Skin Therapy Lett. 2001 Apr;6(7):3-5. PubMed Id: 11376396

Lee NP, Arriola ER. Poison ivy, oak, and sumac dermatitis. West J Med. 1999 Nov-Dec;171(5-6):354-5. PubMed Id: 10639874

Weston WL. Contact dermatitis in children. Curr Opin Pediatr. 1997 Aug;9(4):372-6. PubMed Id: 9300195

Baer RL. Poison ivy dermatitis. Cutis. 1990 Jul;46(1):34-6. PubMed Id: 2143465

Associated Findings

Appearance
No Acute Distress

Body Location
Arm
Cheek
Dorsum of Hand
Eyelids
Face
Forearm
Hand or Fingers
Inferior Eyelid
Leg
Lower Leg
Superior Eyelid
Upper Arm
Wrist

Configuration
Linear
Round

Distribution
Bilateral
Scattered Few
Scattered Haphazard
Unilateral

Exposures
Domesticated Animals
Plant Exposure
Poison Ivy, Sumac or Oak

Lesion
Blanching Patch
Eyelid Edema
Plaque
Scale Fine
Tense Vesicle

Occupations
Farmer
Forestry Worker
Gardener

Signs and Symptoms
No Fever (Afebrile, Apyrexial)
Pruritus (Itching)

Social History
Elementary School (K-5)
Middle/High School (6-12)

Temporal
Developed Acutely Over Days to Weeks