Do oral steroids help with phytophotodermatitis caused by wild parsnip?

Management of Wild Parsnip-Induced Phytophotodermatitis

Oral steroids are not routinely recommended as first-line treatment for phytophotodermatitis caused by wild parsnip, but may be considered for severe cases with extensive blistering or significant symptoms. Treatment is primarily supportive with wound care, analgesia, and topical treatments.

Understanding Phytophotodermatitis from Wild Parsnip

Wild parsnip (Pastinia sativa) contains furocoumarins, which when activated by UV light create a phototoxic reaction on the skin. This is not an allergic reaction but a direct phototoxic effect that causes:

• Initial erythema and burning sensation
• Vesicles and bullae formation (similar to second-degree burns)
• Later hyperpigmentation that can persist for weeks to months

Treatment Algorithm

First-Line Management:

1. Supportive Care:

   • Wound hygiene and gentle cleansing 1
   • Cool compresses to reduce inflammation
   • Adequate pain control with NSAIDs or acetaminophen

2. Topical Treatments:

   • Topical corticosteroids (low to moderate potency) to reduce inflammation 2
   • Moisturizers to maintain skin barrier function

Second-Line/Severe Cases:

For severe, extensive, or highly symptomatic cases (covering >30% body surface area or limiting self-care activities):

• Short course of systemic corticosteroids may be considered (e.g., prednisone 0.5-1 mg/kg for 7 days with tapering over 4-6 weeks) 2
• This approach is extrapolated from management guidelines for severe drug-induced skin reactions

Special Considerations

Differential Diagnosis

Phytophotodermatitis is often misdiagnosed as:

• Contact dermatitis
• Cellulitis
• Fungal infection
• Burns
• Child abuse (in pediatric cases) 3

A careful history focusing on outdoor activities, exposure to plants, and subsequent sun exposure is essential for correct diagnosis 4.

Prevention Strategies

• Avoid contact with known phytophototoxic plants
• Wash skin immediately with soap and water after potential exposure
• Use sun protection (clothing, sunscreen) after potential exposure
• Be particularly cautious in sunny environments where these plants grow 1, 5

Clinical Course

The condition typically follows a predictable pattern:

1. Initial erythematous patches/macules
2. Development of vesicles and bullae
3. Resolution with post-inflammatory hyperpigmentation 4

Pitfalls to Avoid

1. Misdiagnosis: The bizarre, often linear or streaky pattern of phytophotodermatitis can lead to misdiagnosis, particularly as child abuse in pediatric cases 3.

2. Overtreatment: Most cases are self-limiting and resolve with supportive care alone. Systemic steroids should be reserved for severe cases, as they carry their own risks.

3. Underrecognition: Failure to recognize the condition may lead to unnecessary diagnostic tests or inappropriate treatments.

4. Recurrence: Without proper education about causative plants and prevention strategies, patients may experience recurrent episodes.

While there are no specific guidelines addressing wild parsnip phytophotodermatitis treatment, management principles can be extrapolated from guidelines for similar phototoxic and dermatologic reactions 2. The approach should be based on severity, with most cases responding well to supportive care and topical treatments.