Allergic Contact Dermatitis in Workplace

Introduction & Epidemiology - Skin's Workplace War

• Occupational Allergic Contact Dermatitis (OACD): Type IV hypersensitivity reaction to workplace allergens.
• A major occupational illness, causing significant morbidity and economic burden, particularly in developing nations like India.
• Accounts for ~20-25% of all occupational skin diseases.
• Impacts quality of life, leading to absenteeism and potential job changes.
• Common in: Construction, healthcare, agriculture, hairdressing, metal industries.

⭐ Cement (chromium) is a primary cause of OACD in Indian construction workers, especially due to potassium dichromate content in cement.

Pathophysiology - Allergy's Sneaky Setup

• Mechanism: Type IV (delayed) hypersensitivity, with two distinct phases.
  • Sensitization Phase (Initial contact; 10-14 days):
    • Haptens (e.g., nickel, PPD) penetrate epidermis.
    • Combine with skin proteins → complete antigen.
    • Langerhans cells (APCs) present to naive T-cells → memory T-cells formed.
    • No dermatitis at this stage.
  • Elicitation Phase (Re-exposure; 12-72 hours):
    • Allergen re-encounters activate memory T-cells.
    • Rapid cytokine release (e.g., $IFN-\gamma$, $TNF-\alpha$).
    • Results in eczematous inflammation.

⭐ Langerhans cells (epidermal APCs) are pivotal: they capture haptens, migrate to lymph nodes, and prime naive T-cells, initiating sensitization.

Common Workplace Allergens (India Focus) - India's Itch Triggers

⭐ Cement is the most common occupational allergen in India, primarily due to chromate sensitivity. Parthenium is the leading plant sensitizer.

Clinical Features & Diagnosis - Spotting The Reaction

• Morphology:
  • Acute: Erythema, edema, papules, vesicles, bullae; intense pruritus.
  • Chronic: Scaling, lichenification, fissures.
• Distribution:
  • Matches allergen contact area; often well-demarcated.
  • Common: Hands, wrists, forearms, face, eyelids.
• Diagnosis:
  • Detailed history (occupational exposure).
  • Patch Test: Gold standard.
    • Allergens applied for 48 hrs.
    • Readings at 48 hrs & 72-96 hrs (or later for some allergens like PPD, neomycin).
    • Indian Standard Battery (ISB) commonly used.

⭐ Patch testing is the gold standard for diagnosing ACD; positive reactions must correlate clinically with exposure for definitive diagnosis.

Management & Prevention - Worker Skin Shield

• Management:

  • Identify & avoid/substitute allergen (via patch test).
  • TCS for flares; TCIs for sensitive areas.
  • Systemic steroids (Prednisolone 0.5-1 mg/kg) if severe.
  • Antihistamines for itch.

• Prevention (📌 SKIN):

  • Substitute allergens (e.g., ferrous sulfate in cement for $Cr^{6+}$).
  • Keep skin clean; use emollients.
  • Inform & educate workers (hazards).
  • No touch techniques; PPE (gloves, aprons).

• Barrier Creams: Adjunct to PPE, not replacement.

⭐ Cement is a leading cause of occupational ACD, often from chromium & cobalt sensitizers.

• Legislation: Key acts: Factories Act, Employee's Compensation Act.

High‑Yield Points - ⚡ Biggest Takeaways

• Type IV hypersensitivity; delayed onset (24-72 hours).
• Workplace allergens: Nickel, Potassium dichromate (cement), PPD (dyes), Epoxy resins, Rubber chemicals.
• Patch testing is gold standard for identifying specific allergen.
• Features: Intensely pruritic, eczematous lesions (erythema, vesicles) with sharp demarcation.
• Distribution (hands, face) often clues occupational source; improves away from work.
• Management: Strict allergen avoidance is key; topical corticosteroids for flares.
• Chronic exposure leads to lichenification and fissuring.