Original Research

Poison ivy: How effective are available treatments?

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In this study, only one treatment approach significantly reduced pruritus. Three approaches were often associated with recurrences of rash or symptoms.




Purpose To determine the characteristics and clinical course of Rhus dermatitis in patients who seek assistance from primary care clinicians, as well as treatment approaches used by patients and recommended by clinicians, and treatment approaches associated with better outcomes.

Methods This was a prospective cohort study with standardized baseline data collection on patients and their rashes, followed by examination of patient-completed diaries of signs, symptoms, and treatments.

Results Thirty-six clinicians identified 186 interested patients, of which 89 completed and returned diaries and consent forms. Of those 89 patients, 92% reported pruritus; 91%, erythema; 87%, papules; and 49%, vesicles or bullae at baseline. Their rashes involved the head/face/neck, 61%; trunk, 56%; legs, 54%; and arms, 22%.

Patients seeking help for poison ivy can expect the rash to last an additional 2 weeks on average, regardless of the treatment prescribed.From the date of clinical consultation, the mean (standard deviation [SD]; range) duration of any symptom or sign was 14.4 days (8.0; 1-43). Patients most often had tried a topical antipruritic, astringent, or low-potency corticosteroid before seeking care. Clinicians prescribed oral or parenteral corticosteroids 81% of the time, sometimes in combination with a high-potency topical corticosteroid (25%) or oral antihistamine (31%). Only systemic corticosteroids plus high-potency topical corticosteroids were associated with a significantly shorter duration of itching (P=.005). No treatment was associated with reduced duration of erythema, papules, or vesicles.

Conclusions Patients who visit a primary care clinician for Rhus dermatitis can expect the rash to last another 2 weeks on average (total duration: one day to 6 weeks) regardless of what treatment is prescribed. Parenteral corticosteroids plus high-potency topical corticosteroids may reduce the duration of the itching.

Rhus dermatitis (poison ivy, oak, and sumac) is a common cause of contact dermatitis throughout the United States. The condition is usually mild and often not brought to the attention of primary care clinicians. Some patients, however, do see a health care provider for treatment, most often because of pruritus. This form of contact dermatitis results from a type IV hypersensitivity reaction to urushiol, a colorless oil in the leaves, stem, root, and fruit of poison ivy, poison oak, and poison sumac. The reaction, which occurs 24 to 72 hours following contact with the skin, can be prevented by washing the skin promptly with a detergent soap after exposure. By the age of 8, most people are sensitized to urushiol.1

According to most standard texts and clinical reviews, untreated Rhus dermatitis usually resolves in one to 3 weeks. What is not known is whether particular patient or rash characteristics might affect prognosis and thereby influence treatment recommendations—eg, age, gender, race, location of the rash, prior episodes, chronic illnesses such as diabetes, or chronic use of medications such as nonsteroidal anti-inflammatory drugs and corticosteroids.

Impetus for our study. An informal survey of 10 clinician members of the Oklahoma Physicians Resource/Research Network (OKPRN), a statewide practice-based research network, suggested that primary care clinicians treat between one and 10 patients with poison ivy each week during the spring, summer, and fall (median 2.5). Their reported armamentarium included more than 15 different over-the-counter topical agents, several oral antihistamines, and a variety of topical, oral, and parenteral corticosteroids.

Systemic corticosteroids plus high-potency topical corticosteroids reduced the duration of itching.Surprisingly, there is very little published evidence on which to base treatment decisions. Using PubMed and the search terms, Rhus dermatitis, poison ivy, and poison oak, we found only 3 placebo-controlled clinical trials of Rhus dermatitis treatments in the English language literature after 1966. Based on these studies, Zanfel, a mixture of alcohol-soluble and anionic surfactant, may be somewhat effective, but pimecrolimus and jewelweed extract were no more effective than placebo.2-4 There is some evidence that topical corticosteroids are effective only before vesicles appear.5 In one uncontrolled study, intramuscular injection of betamethasone and dexamethasone yielded about a 30% reduction in symptoms within 48 hours.6 Assuming that systemic corticosteroids do produce benefit, however, the most effective dose and duration of treatment have not been determined.7,8

To address some of these gaps in our knowledge base, OKPRN members asked that we undertake a longitudinal cohort study of patients reporting to primary care practices.


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