Lacquer tree dermatitis

Disease Description (Causes and Symptoms)

• Cause: The primary cause is a contact allergy to urushiol (a phenolic antigen) contained in the sap of lacquer trees (lacquer), involving a delayed hypersensitivity reaction mediated by T cells. It does not occur in everyone, and the reaction appears upon re-exposure after sensitization. Ingesting food containing lacquer or inhaling aerosols produced by burning it may cause systemic or respiratory symptoms.
• Pathophysiology: When urushiol comes into contact with the skin, erythema, vesicles, oozing, and itching develop 24–72 hours later as a delayed hypersensitivity reaction. After sensitization, even a small amount of contact can cause a severe reaction, and widespread skin reactions may occur if the antigen spreads throughout the body through the bloodstream.
• Main symptoms:
  • Severe itching (pruritus), rash, vesicles (blisters), serous or bloody exudate, and linear arrangement of lesions (marks of plant contact)
  • Occurs readily in areas with thin or vulnerable skin, such as between the fingers, the armpits, skin folds, the anus, and the perineum
  • Rarely, systemic symptoms such as nausea, vomiting, and dizziness (especially after ingestion), and possible shortness of breath upon inhalation
• Diagnosis: Primarily diagnosed based on clinical findings (exposure history and the form and distribution of the lesions). If necessary, the causative antigen can be identified with a patch test.

Treatment

• Initial first aid
  • As soon as possible (immediately after contact), thoroughly wash the contaminated area with soap and water to remove residual urushiol (effectiveness decreases as more time passes after exposure).
  • Separate and wash contaminated clothing, tools, and pets to prevent re-exposure.
• Topical treatment
  • Mild localized lesions: Use low- to medium-potency topical steroids (low-potency preparations for the face and perineum, and medium- or high-potency preparations for the trunk and extremities, etc.). Calamine lotion and oatmeal baths may relieve itching.
  • Topical antibiotics are not necessary when there are no signs of infection.
• Systemic treatment
  • For widespread lesions; lesions on areas where functional problems are a concern, such as the face, perineum, hands, or feet; or systemic symptoms caused by food ingestion, systemic (oral) steroids may be necessary (as directed by a doctor). An appropriate dose is usually determined, followed by gradual dose reduction (tapering).
  • Antihistamines (sedating or non-sedating) may be used as an adjunct to control itching.
• Treatment of infection
  • If a secondary bacterial infection is suspected (pus, fever, increasing pain, etc.), treat with standard antibiotics for bacterial infections (as determined by a doctor).
• Emergency treatment
  • If there is shortness of breath, severe systemic symptoms, a risk to vision due to involvement around the eyes, or rapid worsening, visit an emergency medical facility (hospitalization, airway protection, intravenous steroids, supportive care, etc.) may be necessary.
• Self-care and precautions
  • Do not scratch (risk of secondary infection), keep the affected area clean, and do not stop high-dose systemic steroids on your own after prolonged use.
  • If lacquer is suspected to have been consumed in food, seek medical advice immediately. Do not burn lacquer or inhale it (inhalation of airborne particles may cause airway injury).
• Prognosis
  • Most cases improve within several weeks with appropriate treatment, but sensitive individuals may experience repeated and increasingly severe reactions upon re-exposure. Airway injury caused by inhalation can be severe and fatal.

Checklist Before an Outpatient Visit (Useful Items to Bring and Example Questions)

• Items/materials
  • A list of currently used medications (including prescription drugs, OTC medications, herbal medicines, and supplements)
  • A history of drug allergies and skin allergies
  • The time symptoms began and exposure history (when, where, and what came into contact with the skin)
  • Photographs of the affected areas (useful for assessing the distribution of lesions)
  • Whether systemic symptoms such as fever, nausea/vomiting, or shortness of breath are present and their severity
  • Whether similar symptoms have occurred previously and the response to treatment (the treatments used and the course)
  • Contaminated clothing or items (if possible, bring them in a bag)
• Information about examinations/treatments that may be provided during an outpatient visit
  • Most cases can be diagnosed through a clinical examination. If necessary, lesion sampling (bacterial culture) or a patch test may be performed.
• Contraindications/precautions before visiting
  • If symptoms worsen rapidly or there is shortness of breath, eye involvement, or systemic symptoms, visiting an emergency room rather than an outpatient clinic is recommended.

Examples of General Questions to Ask a Doctor

• What are the expected side effects of this medication (topical/oral steroids, antibiotics, etc.), and how should they be managed?
• How long is this rash expected to last? How likely is it to recur?
• What safe measures can I take at home to reduce pain or itching (baths, lotions, and substances to avoid)?
• If steroids are necessary, could you explain the treatment duration and how to stop them (tapering)?

Examples of Disease-Specific Questions

• The exposure is widespread or involves the face, perineum, or hands. When should oral steroids be started? (Please include the criteria for the starting dose and treatment duration.)
• If the lesions become oozing or develop pus, are antibiotics necessary? If so, please tell me which medication is used (type of oral antibiotic and duration of treatment).