Prednisone Dosing for Plant Dermatitis (Poison Ivy/Oak/Sumac)
For plant dermatitis (rhus) affecting more than 20% body surface area, prescribe prednisone 0.5-1.0 mg/kg/day (maximum 60 mg/day) as a single morning dose, tapered over 2-3 weeks to prevent rebound dermatitis. 1, 2
Initial Dosing Strategy
- Start with prednisone 1 mg/kg/day (usual maximum 60 mg/day) given as a single morning dose for severe or extensive plant dermatitis 1
- This dosing provides relief within 12-24 hours for extensive allergic contact dermatitis 2
- Avoid underdosing: the commonly prescribed methylprednisolone dose pack (21 tablets over 6 days) provides only 105 mg prednisone equivalent—far below the 540 mg total dose needed over 14 days for adequate treatment 3
Treatment Duration and Tapering
The critical element is a 2-3 week taper, not a shorter course:
- Maintain full dose for 4-7 days, then begin tapering 3, 1
- Total treatment duration should be 14-21 days (2-3 weeks) 2, 4
- One representative regimen: maximum dose for 4 days, followed by 10 mg taper every 2 days 3
- Rapid discontinuation causes rebound dermatitis—this is the primary reason for the extended duration 2, 4
Why Standard Dose Packs Fail
The methylprednisolone dose pack is inadequate because:
- It provides only 84 mg total over 6 days (equivalent to 105 mg prednisone) 3
- This is insufficient for severe contact dermatitis and leads to treatment failure 3
- The short 6-day course without proper taper increases rebound risk 2, 4
Alternative for Limited Disease
For localized plant dermatitis (<20% body surface area):
- Use high-potency topical steroids (clobetasol 0.05% or triamcinolone 0.1%) instead of systemic therapy 2
- Topical corticosteroids can achieve higher effective skin concentrations than oral prednisone for localized disease 5
Important Precautions
- Avoid live vaccines during treatment if prednisone >20 mg/day for >2 weeks 3, 1
- Monitor for hyperglycemia, hypertension, and gastritis during treatment 1
- Patients may have HPA axis suppression for up to one year after even short courses, requiring stress-dose steroids if needed 6
- Do not use chronic or repeated short courses—this increases adverse effects without additional benefit 1