Case

A 13 year old boy comes to the office with the complaint of an itchy rash on his arms, legs, and trunk. He has just returned from a camping trip in Michigan. He says that he wore short sleeves and shorts and always had a shirt on. The rash has areas of linear vesicles. What is the diagnosis and how would you treat this boy?

1. Rhus dermatitis is a cell mediated hypersensitivity reaction that is caused by the exposure to the sap like material urushiol found on the poison ivy, poison sumac, and poison oak.
2. Approximately 50-70% of the general population is sensitized. 
3. The plants are ubiquitous and there are many species with cross-reactivity. 
4. The reaction occurs after contact with the damaged plant that releases the sap like material which binds strongly to the skin. Unless washed off within a few minutes after contact, a reaction will occur. 
5. The greater the sensitivity to the antigen, the sooner and more extensive the reaction. 6.Touching areas of contact can spread the material to other parts of the body that were not initially in contact with the sap and it is important to scrub under the fingernails after contact.

1. The rash usually appears about 24-48 hours after contact but may continue to appear 2 weeks later. 
2. Initially there is pruritis followed by erythema, edema, papules, vesicles, and bullae.
3. Helpful in diagnosing the rash is the linear distribution caused by the branches brushing the area of contact. 
4. Scratching the rash will help spread the lesions and there may be areas of rash where the skin was protected by clothing. 
5. Contrary to popular belief, the fluid from vesicles and bulla do not spread the rash. 
6. The rash can be spread from contact with fomites like shoes, clothing, tools, and from the smoke from burning plants. Animal fur can also be reservoirs of the sap and pets can help spread the antigen if they have been in contact with the plants.

1. Wash immediately after contact, in sensitive individuals within 5 minutes
2. Protect skin by wearing protective clothing
3. Calamine lotion 
4. Topical anesthetics or antihistamines may sensitize the skin and should be avoided
5. Topical steroids are useful for mild cases
6. May need oral steroids for 1-2 weeks. Full dosage for the first week and then taper the second week to prevent rebound
7. Cut the patient's nails
8. Cool compresses may give some relief
9. Oral antihistamines
10. Topical products such as IvyBlock may prevent some allergic reactions by providing aninvisible barrier.  Useful if known sensitive individualis going to area known to have poison ivy.

1. Tunnessen, Walter W.Jr. Poisonivy, oak, and sumac: The three witches of summer.Contemporary Pediatrics June 1985
2. Epstein, Guin, and Mallach  A Poison Ivy Update  Contemporary Pediatrics April 2000