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.     

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.     

Oral hyposensitization to poison ivy and poison oak

We evaluated the safety and efficacy of a 1:1 mixture of pentadecylcatechol (PDC) and heptadecylcatechol (HDC) diacetate in reducing hypersensitivity to poison ivy and poison oak. The study was double-blind, parallel, randomized, and placebo controlled. The 44 subjects receiving the active drug ingested a cumulative dose of 306.5 mg over a five-week period. Subsequently, 14 patients were continued on a maintenance phase, ingesting an additional 960 mg of drug. The PDC-HDC diacetate was well tolerated, with no significant side effects. Evaluation of efficacy compared poststudy and prestudy reactions to patch tests using urushiol in doses of 0.025, 0.05, 0.125, 0.25, and 0.5 micrograms applied to the forearm. The results indicated that the induction phase as well as the maintenance phase did not induce a statistically significant hyposensitivity to urushiol, and we were thus unable to decrease sensitivity to poison ivy and poison oak in humans using orally ingested PDC-HDC diacetate.     

Microbiology of infected poison ivy dermatitis

We report the aerobic and anaerobic microbiology of secondarily infected poison ivy dermatitis. The study involved retrospective review of clinical and microbiology laboratory records of patients with secondarily infected poison ivy lesions. Bacterial growth was noted in 33 specimens. Aerobic or facultative anaerobic bacteria only were present in 18 (55%) patients, anaerobic bacteria only in seven (21%), and mixed anaerobic-aerobic bacteria in eight (24%). Forty-five isolates were recovered (1.4 per specimen): 27 aerobic or facultative anaerobic bacteria, and 18 strict anaerobes. The predominant aerobic and facultative anaerobic bacteria were Staphylococcus aureus (13 isolates) and group A beta-haemolytic streptococci (six). The predominant anaerobes were Peptostreptococcus spp. (seven isolates), pigmented Prevotella and Porphyromonas spp. (four) and Fusobacterium spp. (two). Single bacterial isolates were recovered in 18 (55%) patients, eight of which were S. aureus. Nineteen of the organisms isolated from 16 (48%) patients produced the enzyme beta-lactamase. Organisms that resided in the mucous membranes close to the lesions predominated in those infections. Enteric gram-negative rods and Bacteroides fragilis group predominated in leg and buttock lesions. Group A beta-haemolytic streptococci, pigmented Prevotella and Porphyromonas and Fusobacterium spp. were most frequently recovered from lesions of the finger, face and neck. The polymicrobial aetiology of secondarily infected poison ivy lesions, and the association of bacterial flora with the anatomical site of the lesions, are demonstrated.     

Age differences in poison ivy dermatitis

In both man and animals, cell-mediated immunity diminishes with advanced age, Because poison ivy is a very common allergy, we evaluated age-associated differences in the contact allergic reaction to Rhus. Oleoresin patch tests were applied to two age cohorts (18-25 versus 65-84) each of 14 healthy white subjects. In the elderly, the allergic reaction developed more slowly, the inflammatory response at peak was greatly diminished and the dermatitis lasted longer and seemed to be more pruritic.     

Cost-effective post-exposure prevention of poison ivy dermatitis

BACKGROUND: Poison ivy (toxicodendron) dermatitis is the most common allergic contact dermatitis in the USA. No studies have shown an effect of washing after a short period of time for the prevention of binding of urushiol to the skin. Objective To evaluate the efficacy of three different modes of postcontact prevention using a surfactant (Dial ultra dishwashing soap), an oil-removing compound (Goop), and chemical inactivation (a commercial product Tecnu). METHODS: A consented, unsponsored, volunteer experimental study on medical students from the University of Missouri School of Medicine, Kansas City. Each subject served as his/her own control, comparing four 2.5-cm exposed squares on the inner aspect of the forearm, three of which were treated and one untreated. RESULTS: Comparisons between the different agents were nonsignificant with P > 0.05. Each treatment, however, was significantly improved over the untreated control. CONCLUSIONS: Our study showed 70%, 61.8%, and 56. 4% protection with Tecnu, Goop, and Dial, respectively, when compared to the positive control, or to the possible maximum response, with a cost per ounce (in a local drug and automotive store) of $1.25, $0.07, and $0.07, respectively, for a decrease in protection that is nonsignificant.     

Black-spot poison ivy dermatitis. An acute irritant contact dermatitis superimposed upon an allergic contact dermatitis

A black spot in the epidermis over a blister of poison ivy dermatitis is an uncommon finding. Four patients with the phenomenon are described. Histologic and histochemical studies were made on biopsy material and the blackish deposit on the skin surface was compared with black deposits in and on leaves of the species of poison ivy. This examination revealed a yellow, amorphous substance on the stratum corneum of the lesions and a similar substance in and on leaves of the poison ivy plant, Toxicodendron radicans ssp. negundo. Associated with the pigmentary deposits there were distinct changes of acute irritant contact dermatitis superimposed upon allergic contact dermatitis. Our findings support the view that the black material is the oleoresin of the plant, and that this substance behaves both as an irritant and an allergen.     

Immunologic studies of poisonous Anacardiaceae: oral desensitization to poison ivy and oak urushiols in guinea pigs

Poison ivy and oak urushiols or their components were compared with the respective esterified derivatives for efficacy in oral desensitization of Hartley guinea pigs sensitized to urushiols. The esterified derivatives produced a significantly greater degree of hyposensitization than did free urushiol counterparts. Suppression produced by esterified urushiols was of longer duration than that produced by free urushiols. Groups of sensitized guinea pigs were given high (100 mg/kg) or low (10 mg/kg) doses of a mixture of acetylated, saturated urushiol congeners over a 1-, 2-, or 3-week period. High doses produced a greater degree of hyposensitization regardless of the dosage schedule used. Low doses did not produce significant hyposensitization unless given over a shorter (1 week) schedule. Large single booster doses (33 mg/kg/week) of the acetate derivatives produced a rebound in responsiveness when given, 2 weeks following the last dose of the initial series, to animals hyposensitized with 10 mg/kg. No such rebound in sensitivity occurred in animals given a series of high initial doses.     

Poison ivy/oak dermatitis. Use of polyamine salts of a linoleic acid dimer for topical prophylaxis

Closed patch tests were used to evaluate the ability of 156 different preparations (based on 22 different chemicals) to prevent poison ivy dermatitis. Several polyamine salts of a linoleic acid dimer were identified that were totally able to prevent the usual dermatitis in approximately 70% of subjects. The effectiveness of the preparations improved when the antigen and the protectant were washed off within eight to 12 hours, instead of remaining on the skin for 48 hours. When washed off, and depending on the protectant, concentration, and vehicle used, several of the preparations were totally able to prevent a dermatitis in a range of 56% to 100% of subjects tested. Further work with these compounds may greatly benefit the many people currently plagued by their allergy to poison ivy and poison oak.