Coal Tar Dermatitis

Coal tar dermatitis is skin disease caused by contact with coal tar, pitch, creosote and related products. It includes irritant and allergic dermatitis, phototoxic reactions, tar acne, tar warts and keratoses, and skin cancer.

Exposure. Roofers, road and paving workers, coke oven and gas workers, aluminium smelter workers, wood preservation and railway sleeper workers, and people using tar based medicinal products.

Epidemiology. Uncommon, but risk is persistent where open handling of hot pitch and creosote continues. Sun exposure raises risk and severity.

Sensitivity to light. Polycyclic aromatic hydrocarbons are activated by ultraviolet A, producing burning, erythema and later pigmentation on exposed skin.

Cancer risk. Chronic skin contact is linked to squamous cell carcinoma and, with inhalation, to lung and bladder cancer in coke oven and smelter work.

Pathophysiology.

Polycyclic aromatic hydrocarbons are irritant and, in light, phototoxic through generation of reactive oxygen species. Metabolic activation to epoxides forms DNA adducts and produces mutation.

Allergic disease is uncommon and involves hapten binding with type IV hypersensitivity. Follicular occlusion produces tar acne.

• Erythema, burning, stinging and itching of exposed skin, worse in sunlight.
• Hyperpigmentation (tar melanosis), telangiectasia and skin atrophy.
• Comedones and follicular papules (tar acne); tar warts and keratoses on exposed skin.
• Photophobia, conjunctivitis and corneal irritation after sun exposure.

Red flags.

• Ulcerated, rapidly growing or non-healing warty lesion (squamous cell carcinoma).
• Haemoptysis, haematuria or persistent cough in long term exposed workers.
• Eye pain or visual loss.

• Exposure history including material, tasks, protection and sun exposure.
• Examination of exposed sites, nails and eyes.
• Patch testing with coal tar and photo patch testing in a specialist unit when allergy or photoallergy is suspected.
• Skin biopsy of any keratotic, ulcerated or growing lesion.
• Urinary 1-hydroxypyrene as a measure of recent polycyclic aromatic hydrocarbon uptake in occupational assessment.

Differential diagnosis. Irritant contact dermatitis from other chemicals, allergic contact dermatitis, polymorphic light eruption, actinic keratosis and Bowen disease, photosensitive drug eruption, oil acne.

• Minimise contact: enclosed processes, protective clothing, face protection, coverings for hot pitch and tar, and removal of contaminated clothing.
• Sun protection: broad spectrum sunscreen with SPF 50 or higher applied generously to exposed skin before work and reapplied every 2 hours, plus clothing and shade.
• Hot tar burn: cool with running water for at least 20 minutes, do not pull off adherent tar, soften it later with petroleum jelly or paraffin based ointment, and refer large or deep burns. Update tetanus immunisation.
• Emollient applied liberally at least twice daily, long term.
• Clobetasol propionate 0.05% ointment topically to affected body skin once or twice daily for up to 2 weeks. Maximum 50 g weekly. Monitor skin atrophy, striae, telangiectasia and infection. Avoid on the face, flexures and genitals and on infected skin; use the lowest potency that works in pregnancy and avoid in children.
• Face and flexures: hydrocortisone 1% cream topically once or twice daily for up to 7 days. Maximum 2 weeks on the face. Monitor for atrophy and periorificial dermatitis. Avoid near the eyes with prolonged use.
• Tar keratoses: cryotherapy, or fluorouracil 5% cream topically twice daily for 2 to 4 weeks. Maximum 4 weeks. Monitor erythema, erosion and pain; avoid in pregnancy; use caution with known dihydropyrimidine dehydrogenase deficiency. Biopsy lesions that are thick, ulcerated or growing.
• Squamous cell carcinoma: surgical excision.

Monitoring. Skin examination every 6 to 12 months for life in long term exposed workers; review of eye symptoms and sun protection at each visit.

Referral and escalation. Dermatology for keratoses, suspicious lesions and patch testing; urgent referral for suspected carcinoma; occupational physician for process change; notification and compensation where required.

Special groups. Pregnancy: avoid fluorouracil and use low potency steroids. Fair skinned and older workers need closer skin surveillance.