I know what you are thinking…….he’s blogging about another rash! I think this one though is an important one to recognize and treat. Besides, so many of you have said to me “I’m really bad at rashes!”
What do you think this rash is? What characteristics of this rash make it readily identifiable? If you saw this patient what specific questions would you ask? How would you treat it?
This is a classic rash of poison ivy (oak or sumac.) The key features of this rash are seen in the photo above. The rash has a vesicular and component. Another key feature is the areas of linearity and “crisscrossing.” The rash usually develops within 24 to 48 hours after exposure. Contrary to popular belief, the vesicular fluid contains no antigen and is not responsible for spreading the rash.
If someone is exposed to poison ivy, they should immediately irrigate the area. It should be noted that at 10 minutes after exposure, only 50% can’t be removed. This decreases with additional time up to 30 minutes when all of the oil is absorbed.
There are several over-the-counter products available for post exposure prevention of the rash. Tecnu and Zanfel have demonstrated promising results but the number of subjects studied was low (n=20 and 24 respectively.)
When the patients present with poison ivy, treatment is directed at control of pruitis and limiting the duration of symptoms. There are many over-the-counter products available for control of pruritis. Tepid baths with baking soda or colloidal oatmeal, cool compresses, and calamine lotion are common effective treatments. Oral antihistamines such as benadryl or atarax is also effective.
The mainstay of treatment for moderate or severe poison ivy is systemic steroids. When the poison ivy becomes significant enough to require steroids ( I tend to use more than one body part as my gauge,) the risks of application of topical steroids outweighs the benefits. The most common mistake I see with poison ivy treatment is giving too short a course of prednisone. The suggested length of treatment is 10 to 12 days. The taper I use is as follows:
Days 1-3: 60mg qd
Days 4-6: 40mg qd
Days 7-9: 20mg qd
Days 10-12: 10mg qd
To summarize, we will be seeing patients in the coming weeks with poison ivy as the weather is getting nicer. The rash is easy to identify in most cases with history of exposure. Remember that the rash will usually be linear in places and will usually have vesicles present at some point. Make sure you recommend symptomatic control and extend your steroid taper to 10-12 days.
I have included two articles to review in case you’d like to read more on the topic.
- Gladman, A. Toxicodendron Dermatitis: Poison ivy, Oak, and Sumac. Wilderness and Environmental Medicine. 17 (2006)120-128
- Sasseville, D. Clinical Patterns of Phytodermatitis. Dermatology Clinics. 27 (2009) 299-308