Some background reading on poison ivy

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Following up on Scott D's comment recommending Zanfel, I found this very interesting review article on poison ivy-induced dermatitis. Probably the most interesting bit is:

Systemic steroids are the standard treatment for severe Toxicodendron dermatitis. The typical dose of oral prednisone is 0.5-2.0 mg/kg/day (usually 1.0 mg/kg/day) tapered over a 14-21 day period.2, 6, 8, 34 Based on the results of one study,50 three-weeks is a reasonable duration, although this aspect of treatment is debated. If steroids are stopped earlier than 14 days after onset of dermatitis, the eruption will "break through".3 Alternatively, intramuscular triamcinolone acetonide, 1.0 mg/kg, naturally tapers over 3-4 weeks and, in the author's experience, compliance is 100%,35 and there are less acute side effects such as emotional lability, water retention, hyperactivity, and increased appetite. Rare side effects of corticosteroid use include exacerbation of gastric ulcers, diabetes, hypertension, and rarely, avascular necrosis of the hip.49 Corticosteroids decrease inflammation by reversing increased capillary permeability and by suppressing neutrophil activity. Corticosteroids reduce itching by inhibiting a delayed type hypersensitivity response.

...

While systemic steroids are extremely effective when indicated, it is common for patients to seek further treatment for Toxicodendron dermatitis after receiving a dosepak of methylprednisolone. This 6-day treatment regimen contains the equivalent of 30-25-20-15-10-5 mg of prednisone on each of the six days. This is a lower and shorter dose than will effectively treat Toxicodendron reactions.8, 49 The dermatitis 'recurs' because it requires at least 3 weeks to run its course,50 and stopping the steroids merely allows the natural disease to "come out of hiding."

This appears to be a fairly common mistake. I've been prescribed dosepaks before, and at least once noticed the rebound effect. Clearly this is something to mention if you have to go to the doctor for steroid treatment. The only article I was actually able to get a copy of was:

Brodell RT, Williams L. Taking the itch out of poison ivy. Are you prescribing the right medication? Postgrad Med. 1999;106:69-70.

This article cites a bunch of others (note that I haven't been able to actually get copies of them):

Ives TJ, Tepper RS. Failure of a tapering dose of oral methylprednisolone to treat reactions to poison ivy. JAMA 1991;266(10):1362
Baer RL. Poison ivy dermatitis. Cutis 1986;37(6):434-6
Wooldridge WE. Acute allergic contact dermatitis: how to manage severe cases. Postgrad Med 1990;87(4):221-4
Funk JO, Maibach HI. Horizons in pharmacologic intervention in allergic contact dermatitis. J Am Acad Dermatol 1994;31(6):999-1014

To make things even better this article claims that oral antihistamines don't help the dermatitis at all (there's actually a controlled trial indicating that they don't) though they may make it easier to sleep. As I've long suspected, neither does 1% hydrocortisone cream. Hydrocortisone cream + oral antihistamines is of course the standard treatment you get if you show up at your doctor with poison ivy. Topical antihistamines don't work either.

As for Zanfel, there's a single controlled trial that indicates that it works early on and an apparently uncontrolled one that indicates that it works four days after exposure. I don't have any reliable anecdotal data one way or the other.

3 Comments

Scott in the previous post is right about Zanfel. Hard to find and expensive but it works. We live in the santa cruz mountains and are well aquainted with the joys of poison oak. Except for one horrible case my husband got a few years back where it got into his bloodstream and broke out all over his body zanfel has cleared up every poison oak rash both of us has had within 24 hours.

Before we found zanfel we had tried everything on the market -- tecnu was the best we had found and that only works if you wash with it just fter you're exposed. Zanfel works days after if you don't know if you've been exposed or if it gets on your clothes and hits you later. It is miracle stuff.

Hey!!! Does my previous comment not count as anecdotal evidence just because I'm Canadian? :-)

I ended up going for the Zanfel about six days after I picked up the poison oak scrapes (and maybe two days after the onset of symptoms). The Zanfel was less than a miracle, but it did buy me a few hours of 100% relief every time I used it.

(There was tons of poison ivy back in Eastern Ontario, and I'd always thought that I was not allergic to it... until I had this bout with poison oak here in CA.)

The predinose information is interesting. If I recall correctly, I only got a 5 or 7-day dosage of prednisone from the ER, and it was constant dosage over time. If I were smarter and wiser, should I have asked for something else, like this dosepak thing, but followed up with some low-dosage junk to prevent the rebound?

Sorry, I meant that I didn't have any *personal* anecdotal evidence. There are certainly lots of testimonials. I'll have to look up what the recommended steroid protocol is, but IIRC it's a 3-week taper rather than a 1 week one.

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